Surveying - An Introduction

Surveying :- Surveying is the that branch of science which deals with the art of determining the relative positions of points on , above or beneath the surface of the earth by means of an direct measurement or indirect measurement of direction , distance and elevation. It also includes the art of establishing points by predetermined angular and linear measurements. The application of surveying requires skill as well as the knowledge of the  mathematics , physics and to some extent , astronomy.

Levelling :- Levelling is a branch of surveying which deals with the object of which is -
1. to find the elevations of points with respect to a given or assumed datum , and
2. to establish points at a given elevation or at different elevations with respect to a given or assumed datum. The first operation is requires to enable the works to be designed while the second operation is required in the setting out of the all kinds of engineering works. Levelling deals with measurements in a vertical plane.
The knowledge of surveying is advantageous in many phases of engineering. The earliest surveys were made in connection with land surveying. Practically , every engineering project such as water supply and irrigation schemes , railroads and transmission lines , mines , bridge and building etc. requires surveys. Before plans and estimates are prepared , boundaries should be determined and the topography of the site should be ascertained. After the plans are made , the structures must be staked out on the ground. As the work progresses , lines and grades must be given.
In surveying , all measurements of lengths are horizontal , or else are subsequently reduced to horizontal distances. The object of a survey is to prepare plan or map so That it may represent the area on a horizontal plane. A plan or map is the horizontal projection of an area and shows only horizontal distances of the points. Vertical distances between the points are , however , shown by contour lines , hachures or some other methods. Vertical distances are usually represented by means of vertical sections drawn separately.

Geology - Interior of the Earth

Lithosphere :- The solid Earth is known as Lithosphere. An idea about the constituents of this solid body of about 6370 km radius , can be had on the basis of several available indirect observations. Say for example , the average density of the whole earth is 5.5 , whereas that for the rocks making most of the upper crust of the Earth is 3 , which infers that the material beneath the surface is of a much higher density. The temperature indications show that it increases with the depth. The hat lava erupted by the volcanoes also indicates that the deep interior parts of the Earth are very very hot. The pressure as also been observed to be increasing with depth. An analysis of the meteorites falling on earth indicates that they essentially consist of iron and nickel in their core. Since the earth is also a celestial body like That of the meteorites , it can be easily inferred that out of Earth may also contains iron and nickel in it's core.
From all such indirect evidence , it has been generally established that the matter inside the earth is of a higher density , and the deep interior part of the Earth may be in liquid state ; or because of high pressure , it may be in semi-liquid state.
In the modern times , however , our knowledge regarding the interior of the Earth has been vastly increases by the experimental results obtained with the help of seismic waves. During an earthquake ( natural or artificial produced by an explosion ) , three types of waves are generated , known as primary (P) , Secondary (S) , and Long (L) waves. These waves radiated in all directions passing through the earth body , moving faster in the higher density medium. The L - waves which confines themselves to the crystal part , travel faster along the ocean floors. This indicates that the ocean floor composed of a material denser than that of the upper crust of the continent basins. The P and S waves which propagate through the deeper parts of the Earth , are subjected to reflection and refrection with the changes in density. The S-Waves are further characterised by their capablity of passing only through the solids. 
Based upon such experimental work, carried out with the help of such seismic waves , the interior of the Earth can be predicted today , with an enough degree of confidence.
In all , the entire 6370 km thickness of the Earth can be divided into the following three major zones :-
(A) The Crust
(B) The Mantle
(C) The Core

(A) The Crust :- The topmost thin layer of the earth body , having solid thickness of about 30 to 40 km In continents and 5 to 6 km in the oceans , is known as the crust. The base of the crust is marked by a sharp boundary , called Mohorovicic discontinuity or M - discontinuity. The depth of the M - discontinuity is greater beneath the continents than beneath the ocean basins.
Intact , it has been concluded that in the continents , the total depth is about 35 km , out of which the bottom of 5 km depth consists of denser Basalt rock ( density = 3.0 ) , and the top 30 km consists of lighter Granite rock ( Density = 2.7 ) . There is no such granite beneath the oceans , and only 5-6 km thick basalt occurs. These granitic rocks of the continents and the basaltic rocks of the oceans , are generally covered by a top layer of unconsolidated sediments deposited since the formation of these continents or oceans.
The earth crust thus provides us with very useful hard and soft rocks , and are classified as , Igneous , Sedimentary , and Metamorphic rocks , depending upon the certain factors.

(B) The Mantle :- Beneath the M - discontinuity , lie the still denser rocks ( average density 3.3 ) known as the ultra basic rocks , and this portion of the earth is known as the Mantle. It's thickness is about 2860 km and it's density increases with depth.

(C) The Core :- Below the depth of about 2900 km from the surface of the earth , starts the cores. It has been inferred by the study of seismic waves that the earths core is probably 12 or more , but it's exact compositions is not known. Most of the scientists is favour in iron - nickel composition , while some other support the idea of iron - silicate core.
An abrupt increase in the velocity of P - waves at about 2170 km below the core boundary , suggests the presence of an inner core.
This may mean a change from the liquid to the solid state , but this is not well established fact.
The presence of earth's magnetic field may also be explained under this theory of the presence of a liquid core. This may be due to the electric current set up by motion in the liquid core. This is possible because the core is thought to be metallic and , therefore , a good conductor.

Geology - The Exterior of the Earth

We know that the gaseous layer encircling the Earth outside it's surface is called the atmosphere. This gaseous environment extends to about 500 km beyond the Earth surface. Although , extending to far such large distances , this atmosphere weighs only about one millionth part of the weight of the Earth. This is because of its gaseous composition.
This atmosphere has been established to be consisting of layers of different environments. As such , it can be divided into the following four zones :-

(1) Troposphere :- It is the nearest gaseous zone extending from the surface of the earth upto a average distance of about 11 km at the poles and 17 km at the equatorial regions.
Temperature decreases with the height in the troposphere , since the main heat source is the solar radiations which is absorbed at the ground level. The rate of decrease of temperature , called the lapse rate , is about 5* C/km. The troposphere contains most of the water vapour , clouds , and storms of the atmosphere Winds tend to be the strongest at the tropopause , the level of the jet streams. This is also the level at which the jet aircrafts cruise. The troposphere contains about three-fourth of the total weight of the atmosphere, and is responsible for the most of the meteorological processes. Thus it is the troposphere , in which winds are generated and clouds are formed , which cause precipitation.

(2) Stratosphere :- Above the tropopause (at about 10-16 km altitude) lies another zone , called the stratosphere , extending upto about 50 km altitude , to a point called the stratopause. Between the tropopause and stratopause , the temperature increases gradually with height , from about - 80*C to about 0*C or so. At the stratopause , the temperature , infact , is about as heigh as at the ground level. It's warmth due to the absorption of ultraviolet radiation from the sun by oxygen and ozone. Most of the worlds ozone is found in the stratosphere , where it may exceeds 5 ppmv (parts per million by volume). Hence , stratospheric air is lethal to human beings. There is very little water vapour at these heights. Ozone is , infact , formed in this zone due to the splitting of an oxygen molecule into the atomic oxygen and it's subsequent union with an oxygen molecule to form Ozone. Ozone is , however , destroyed naturally by ultraviolet radiation , as it helps in preventing ultraviolet radiation from the reaching the ground. In the stratosphere , ozone is , thus , constantly being formed and destroyed , and is , therefore , maintained in a rough equilibrium , under natural unpoluted environment.
Since , ozone is formed in the stratosphere , this zone is also sometimes called as the ozonosphere. The ozonosphere is of utmost importance to life on the Earth. As it absorb most of the ultraviolet radiations from the sun , which in its absence , would possibly have burnt all the life on Earth.

(3) Mesosphere :- The Mesosphere extends from the stratopause at about 50 km altitude and at about 0* C to another temperature minimum of about - 110* C at about 80 km altitude. This top boundary of Mesosphere is called mesopause. The atmosphere in this zone is windy and turbulent , but there is usually too little water vapour for clouds to form.

(4) Thermosphere :- Above the mesopause ( 80 km altitude ) the temperature increases indefinitely upward into the Thermosphere ( I.e the hot upper atmosphere ) , which zone may extend upto about 500 km altitude.
The Mesosphere and the Thermosphere zones contains many ions and free electrons. Cosmic rays and radiations from the sun produces these ions. Both these zones together are , therefore , usually referred to as the ionosphere. The ionosphere is very light in mass , despite having a large volume.
The region of atmosphere beyond about 500 km , is called exosphere , and till today , very little is known about it. It is perhaps a low density , high temperature region , with minimum atomic collisions.
As far as the chemical compositions of the atmosphere is concerned , it has been found to be mainly a mixture of approximately 78% Nitrogen and 20% oxygen by volume. Other gases like carbondioxide , argon , neon , helium , ozone and water vapours will be constitute the balance 2 % . This consumption is fairly constant in the region of troposphere and a large part of stratosphere. Dust particles and liquid droplets are also found present in the lower atmosphere , and water vapours may be present in large variation.

GEOLOGY - The Possible End of the World. How and When ?

What is the future and fate of the unique planet on which we live ? This is a question which the scientists are trying to answer in the modern days of advanced technology. Well intact , with any amount of advanced science , it is not possible to give a correct precise answer to this question. What actually will be the end of our earth , is the question which time alone will tell. Man , however , due to his inherent curiosity , cannot wait and see , and is therefore , trying to speculate or theorize on this issue , just as he did on the issue of the origin of the earth.
Many astronomers have tried to find out suitable answer to this riddle. Most of them try to connect the life of the earth with the availability of heat and light from the sun. Indeed , if we were not so much depend upon the sun , perhaps , in most probability , the earth might have last for ever.  But since , earths life is very much dependent upon the sun , it will possibly end , as and when the Sun's nuclear fuels gets exhausted and it stop radiating energy.
On the basis of the studies of the older stars that resembles our sun , it has been seen that when the aging stars begins to run out their nuclear fuels , they starts burning and ultimately become dark. On the same analogy , our sun also be one day behave in the same fashion , and thus in most probability , the end of our earth will come in the following manner :-

When once the original hydrogen of the sun gets converted into helium , it's core will begin to contract. And as the core shrinks , it will generate sufficient heat to start thermonuclear reactions capable of producting incredibly high temperatures. These nuclear furnaces may cause the body of the sun to expand , and thus gradually increasing the amount of heat and light radiation. This accelerated radiation should cause the sun to become hotter and hotter , and redder and redder , till it becomes a red giant-a mass of red hot , rarefied gas. During this stage of expension of the sun and it's great heat releasing powers , the two nearby planets I.e Mercury and Venus may completely get vaporised and lost. As regards the 3rd and 4th planets I.e Earth and Mars is concerned , it is possible that they may also get vaporised , may avoid that fate in Toto due to their greatest distance from the sun. In any case , the earth will not escape the deadly high solar temperatures , the oceans will boil , the rocks melted , and life destroyed.
The future of our sun and earth upto this stage is quite certain although scientists cannot precisely define the events that would follow this. In all probability , after reaching the climax of hot red gaint , the will steadily diminished in brightness and energy , and end itself into a white dwarf. This is possible , because we have seen stars that have completely exhausted their supply of hydrogen and other nuclear fuel , and shine only because of their internal heat. As a white dwarf , the sun will continue to radiate its energy , and will gradually get cooled and contracted. In due time , it will probably shrinks to the size of a planet , and become cold and dark.
With its fires gone out , the sun and planets of the solar system will become at the mercy of the icy temperatures of the interstellar space. At these temperature of hundreds of degrees below the freezing , gases will be converted into liquids , and liquids will become solids , and thus , earth will eventually become a dark frozen mass.
It is , however , very much possible that even in death , the sun will continue keeping its hold on the remaining planets , which will continue to revolve around this cold inert sun. This is because the sun's mass and gravitational force will remains strong enough to keep the remaining planets locked in eternal orbits around it.
After predicting , as to how the earths end will come , we are now left with the possible timing if this occurrence. When will these predicted solar changes occur ? Well , the present and nearby population of the world has no cause to worry , because it's seems possible that the life on earth will further continue to flourish for at least 5 billions years , perhaps even longer. This time period has been based on the assumption that medium sized stars , like the sun , radiate at least 10 billions years , before the hydrogen fuel of their core is exhausted. Thus , the sun , which , at present , is about 5 billions years old , is in its 'middle age' and will continue for a further period of about 5 billions years.

GEOLOGY - Earth and Origin of Earth

We know that the Earths place in the universe is indeed small , and compare to the other planets , it is not too large in size. Even inspite of that , Earth is a sizeable body , with a polar diameter of about 12, 714 km , and equatorial diameter of 12,756 km , and thus has an equatorial bulge. The circumference of the earth is about 40, 000 km , and it's surface is area is about 510 million square km. Its volume is about 1042 billion cubic km , and it's mass is about 5.97 into 10 is power 21 tonnes. In shape , the earth is like an oblate spheroid. That is , with the exception of a slight flattening at the poles , the earth is nearly spherical or ball shaped. The minor flattening or earth's equatorial bulge is caused by the centrifugal force of rotation. This midriff bulge of earth is very minor in the sense that on a model earth of 8 metre in diameter , one could hardly see it , for this slight protuberance would amounts to less than 2 cm. On the same scale ,  our highest mountains would rise to about 1/2 cm above the sea level.
But deposit it's relatively unassuming statistics , ours is a most fortunate planet the seems "just right" in many ways. Its general size , composition , daily rotation and it's distance from the sun perhaps provides optimum conditions for the development and continuation of life. The fact that earth is the only planet that appears to have a large supply of water , has undoubtedly had much to do with this. Earth's No. 3 position is also very important , for at about 150 million km from the sun , it is neither too near it , nor too far off it. Has it been very near to the sun like mercury , the heat and temperatures would be enormously high and seas would have literally boiled away. On the other hand , if it would have been too far away like Pluto , there would be incredibly cold , making life impossible. Earth's average of temperature of 14 degree celcious appears to be "just right" for life sustenance.

Origin of the Earth :- We human beings have been living on the Earth for a very long time. During the development of science on the Earth, and in his search to know the unknown, man has thought to a lot to know as to how Earth was born. Where from it come ? This question , which has kept the minds of the cosmogonists agitated for a long time , can not be answered with certainty , even till to day.
Infact , the problem is not only to predict the origin of the Earth , but is to predict the origin of the entire solar system , of which , Earth is an important member. Therefore , any speculative suggestion made on the mode of this origin , must satisfy all the known facts about our solar system , and it must agree quantitative with all the known physical and chemical laws.
Intact , our solar system is a well ordered system of planetary bodies , and is not just a haphazard arrangement. This fact may indicate a common origin for all the components of this system. Hence , the entire solar system should be viewed as a whole together , abducted any prediction made regarding the origin of any of its component should be satisfy all the known characteristics of the entire solar system as a whole.

GEOLOGY - Universe and the Solar System

The earth on which we are living is a 'remarkable' astronomical body in the entire universe , even though it is neither the largest or the heaviest , nor the fastest or the slowest member of our solar system. It is , intact , a very insignificant component of our solar system , which consist of nine major planets (including the earth) moving around a central body - the sun. Besides these nine major planets, there are 32 moons or satellites , vast number of asteroids , thousands of comets , and innumerable meteors , which constitute the integral part of our solar system. The nine major planets and their moon's are revolving in nearly the same plane around the sun. In addition to this movement around the sun , these planets are undergoing constant rotation about their own axis. The inner four planets , in the order of increasing distance from the sun are :-
(1) Mercury
(2) Venus
(3) Earth
(4) Mars

The outer group consists of :-
(5) Jupiter
(6) Saturn
(7) Uranus
(8) Neptune and
(9) Pluto.

The four inner planets are also known as terrestrial planets because they are about the same size , and their density suggests a composition of iron and stone. They are , thus , characterised by relatively smaller mass , much higher average density and faster speeds of rotation. These four planets have also been referred to as minor planets. The five outer planets are the major planets which reassemble the terrestrial planets , but are usually treated as a separate group. They are characterised by heavy mass , much lighter in average density , and sluggish in speeds of rotations.
Astrologers agree that all the major planets have already been discovered. The latest and the most recent discovery was that of the planets Pluto , the farthest planet from the sun , and whose position in space was predicted by astronomers more than a decade before the actual discovery in 1930. The only planet , for which no moon's are known are Mercury , Venus and Pluto. The earth has only one , whereas Saturn has ten , and Jupiter has twelve ; Mars and Neptune have two each , and Uranus has five.
Even inspite of the fact that the earth is a very insignificant component of our solar system , and much more insignificant part of our universe , it has been termed as 'remarkable' , mainly because of the fact that out of billions of celestial objects in the universe , it is the only body which is certainly known to support life , as we know it today. It also becomes of important to us because it is our home and we live on it.  It also becomes important to us because it is our home and we live on it.

-: Satellites or Moon's are those celestial bodies , each of which are revolving around any of these nine planets.

-: Asteroids are the minor planets , generally situated between the orbits of Mars and Jupiter. The largest of these bodies probably exceeds 700 km in diameter , and the smallest visible Ones are 2 to 3 km across.

-: Comets are the heavenly bodies having a long tail pointing approximately away from the sun , and a brighter head section that contains a small bright nucleus.

-: Meteors are smaller solid bodies moving through the space , and getting illuminated while entering earth atmosphere.

GEOLOGY - Around Us

If we start thinking in terms of geology , we will always find geology around us. Whether we are walking through the fields ; or driving through the country ; or standing near a temple or a building ; or sitting at a place , we will always be incontact with the processes and materials of geology. For example , pick up a piece of Limestone rock. There will probably be fossils in it , which may well represent the remains of the animals that lived in some prehistoric sea , which once covered the area.
Similarly , say for example , we are walking along a river bank , and notice the silt , which has been left on the bank by the river floods. This should , in geological parlance , remind us of the ability of the running water to deposit sediments - sediments that may on a later date be transformed into rocks. At the same place , if we notice , we can find the scoured river banks , which have been eroded by the swift water currents. This will indicate , as to how the soil has been removed by erosion - a geological process , which is so very important in shaping of various features of our Earths surface.
Sometimes , you may notice a field of black fertile soil supporting a fine crop of corn. You may be surprised to know that this dark rich soil may have been derived from an underlying chalky white Limestone - still another reminder of the importance of Earths material in our every day life.
Sometimes , you may be sitting or standing a near a building or a temple , where you will notice a various types of stones used in flooring ; or in face work ; or in a structural members. Will you not like to know as to what are rocks are they , where are they found , and what are their strengths and costs ? All these details shall indeed be provided by the study of geology.
Geology , therefore , concerns with our daily life , and is the most interesting and useful subject for a layman as well as for knowledgeable people like you. One must know , if not in a specialised manner , then atleast in a general way , something about geology. The engineers , particularly the civil engineers - who have to use the rocks for construction purposes , and the grounds (soil and rocks) for supporting their engineering structures like dam's , roads , bridges , railway tracks , docks and harbours , tunnels , etc. must have a good and a through knowledge of the subject. Similarly , the mining engineers , who have to mine the rocks , to take out ores and other rocks for their various economic and building uses , must be well aware of this subject.

GEOLOGY - Scope of Geology

The scope of geology is so broad that it has been split into two major division : (1) Physical Geology. (2) Historical Geology. Each of these divisions , have for convenience of specialised study , been further sub-divided into various branches or sub sciences. The term Earth science is commonly used in conjunction with the study of the Earth ; although Earth science includes the study of geology , and also encompasses the science of meteorology (the study of the atmosphere), oceanography (the study of oceans), and astronomy of course.

<b>1. Physical Geology :-</b> Physical geology deals with the Earth's composition , structure , the movement with in and upon the Earth's crust , and the geologic processes by which the Earth's surface is, or has been changed. This division of geology includes in itself , the following branches :-

(A) Mineralogy :- The mineralogy , obviously deals with the study of minerals. Minerals are the basic constituents of rocks , and thus , influence the properties of the rocks. Hence , in order to know the properties of the rocks , one has to study the properties of the minerals. In mineralogy , therefore ,  the mode of formation , composition , occurrence , types , association , properties , uses etc. of the minerals , shall be studied in details. This study will helps the civil engineers to know as to why the rocks like Quartzite and Marble , which though resemble in shine , colour and appearance , yet differ widely in their behavior ; Quartzites being very tough , strong and durable ; while Marbles disintegrate and decompose in a shorter period. This happens so , because of the difference in their mineral composition.

(B) Petrology :- The term Petrology is derived from the Greek word , Petro + logos. Petro means rocks and logos means study. Hence , petrology means the study of the rocks. Since the earth crust, also called lithosphere , is composed of different types of rocks , their study is under this branch , which deals with the study of mode of formation , structure , textures , composition , occurrence , types etc. of the various rocks of the Earth's crust.

(C) Structural Geology :- The rocks which constitute the Earths crust , have undergone and continuous to under go various deformations , dislocations under the influence of tectonic forces ; causing formation of geological structures like folds , faults , joints , unconfirmities etc. in the dark masses .

(D) Geomorphology :- This branch of geology explains and studies the origin of various surface features of the Earth.

(E) Economic Geology :- This is a specialised division of Mineralogy and Petrology , where in the product of the Earths crust having good economic value , are studied. Valuable ores , containing metals, like diamond , gold etc. economical minerals are like coal , petroleum , etc. do come under the domain of this specialised study. It includes the study of their occurrence , search and exploitation for commercial and industrial uses.

<b>2. Historical Geology :-</b> Historical geology deals with the study of origin and evolution of the earth and it's inhabitants. Like physical geology , this division of geology has also been bifurcated into several branches , due to the variety and vastness of this field. Each of these branches is actually a science in its own right , and one may devote a lifetime to study the specialised subject in any one of them. The various sub-division of this branch of geology includes :

(A) Stratigraphy :- These studies help in working out the geologic history of an area , and is concerned with the origin , composition , proper sequence , and correlation of the rock strata. The term Stratigraphy has been derived from the Greek words : strata + graphy. Strata means the sets or beds of sedimentary rocks ; while graphy means the description. Hence , this branch of science deals with the study of the beds of the sedimentary rocks. The study of such rocks gives an indication of the time that has passed since their formation ; thereby indicating the life history of the rocks and of the earth and it's inhabitants. The study of these rocks will also involved extraction of fossils , I.e the remains of plants and animals of the past geological Eras.

(B) Palalentology :- Palalentology deals with the study of the ancient organism , plants and animals etc. as revealed from there remains and remnants. This study helps in providing a background to the development of life on Earth , over the past geological eras.

(C) Palaeogeography :- This branch of science deals with the study of the geographic conditions of the past times. It, thus deals with the reconstruction of the relations of the ancient lands and seas , and the organism that inhabitanted them.

These branches of historical geology are , intact interconnected with each other , and overlap also in various respects ; as in the case with the various branches of physical geology.

GEOLOGY - An Introduction

We live on a wonderful planet, called the Earth , yet how little most of us really know about its composition and history. We consume the products of soil which have been formed by the weathered rocks ; we use coal, natural gas and oil formed from the remains of pre-historic plants and animals ; we enjoy the beauty of precious stones. But these are only a fraction of the valuable materials, which have been bestowed on us, by the Earth. Think of the importance of the Earths products in the development of modern industries. Our vast mineral resources , such as lead , iron , coal and petroleum are derived from the earth, and these basic products have been made available to us easily , by the application of science , which deals in the study of the Earth. This science , which deals with the study of the Earth , is known as Geology. The term "Geology" has been derived from the Greek words Geo + logos. Geo means earth , and logos means discourse or study or science. The subject of "Geology" , therefore, deals with the study of the wonderful planet 'Earth' , on which we are living. The science of Geology tell us about the origin , structure and history of the Earth and its inhabitants , as recorded in the rocks. Without its study , one remains ignorant about the same planet on which one is living.
The Earth has not only provided us with the minerals and other products , which are used and consumed by us ; but has also provided us with so many scenic things, which we call as the products of 'nature' or 'God'. The areas of exceptional beauty , like the great mountains , the deep awesome gorges , the fascinating lakes , the charming springs , the marvellous coral reefs , the spectacular volcanoes , the stupendous water falls , and what not. Even the man itself is a product of Earth and its surrounding environment. All these and many more things are the results of geological processes that are still at work within and on the Earth , even today. They are the same processes which began to shape the earth soon after its birth some four or five billion years ago.
The event of July 1969 took Geology out of its originalsphere , and plunged it into space Age : man had set foot on the moon and brought back samples of moon rocks for the geologist - the Earth scientist , to study. Who knows to what such studies will lead ? Shall we have a clearer picture of the origin of both moon and Earth ? Shall we find on the moon , rich mineral deposits, or minerals as yet unknown to us.
Perhaps , we will be visiting other planets with in our solar system in the coming years ; this too , will create fascinating new branches of geology.
But now , let us return to our own planet. To a geologist , the earth is not a simple globe , upon which we live ; it is an ever - present challenge to learn more about such things as earthquakes , volcanoes , glaciers and the meaning of fossils. How old is the earth ? Where did it come from ? Of what is it made of ? What will happen to it in future ? To answer such questions , the Earth scientists (geologist) must study the evidence of events that occurred millions of years ago. He must then relate his findings to the results of similar events that are happening today. He tries , for example , to determine the location and extent of ancient oceans and mountains , and to trace the evolution of life as recorded in the rocks of different ages. He studies the composition of rocks and minerals forming the crust of the Earth , in an attempt to locate and exploit the valuable economic products that are to be found there. In perusing his study , a geologist heavily relies upon other basic science such as astronomy , chemistry , physics , biology , zoology , botany etc. For example , astronomy , which deals with the study of the nature and movements of planets , stars and other heavenly bodies , tells him as to where the earth fits into the universe , and has also suggested several theories as to the origin of our planet. Chemistry , for example , deals with the study of the composition of substances and changes which they undergo , helps a geologist in analysing and studying the rocks and minerals of the Earths crust. The science of physics , which deals with the study of matter and motion , again helps a geologist to interpret and explain the various physical forces affecting our Earth , and the reactions of the Earths material to these forces.
Similarly , to understand and interpret the per-historic plants and animals , a geologist takes the help of biology , which deals with the all living forms. Similarly , Zoology provides him detailed information about the animals ; and botany gives insight into the nature of ancient plants. By using all these sciences as well as others , a geologist is better able to cope with the many complex problems that arise in the study of the Earth and it's history.

Economics and Management - Theory of Production

Satisfaction of human wants is the main objective of all economic activities. Human wants are satisfied with material and non-material goods. Consumption is possible only when these material and non-material goods are available. That activities which makes goods available is called production. It is production that makes available wealth in the forms of goods and service for consumption. That unit which is engaged in the fact of Production is called a firm or a producer.

- Production Function :- Production function expresses the physical or technical relationship between the quantity of good produced and the factors of Production necessary to produce it.
Types of production function :-

1. Production function due to change in factor proportion.
2. Production function due to change in scale.
3. Production function due to change in factor proportion and scale.

Laws of Production :- Output of any good depends upon the quantity of inputs and techniques of Production. If a producer desires to change the amount of his output, he can do so by making a change in his inputs. When a producer effects a change in his production by increasing or decreasing only one factor of Production and as a result there is a change in the proportion of combination of factors of production, then this proportional relationship between production and factors of Production (inputs) is refered to as Law of Variable Proportions or Law of Returns to a factor.

- Fixed Inputs or Factor of Production :- A fixed Inputs or factor of Production is defined as one, the quantity of which can not be changed in the short run as the level of output changes. Some examples of fixed inputs are plants , major equipments, buildings , service of management and supply of skilled labour.

- Variable Input or Factor of Production :- A variable input or factor of Production is defined as one the quantity of which may be changed in the short run as the level of output changes. Some examples of variable inputs are raw materials and labour services.

- Time Period :- It may be worth noting that fixity or variability of inputs or factors depends upon period of time available for the adjustment of inputs in accordance with the changes in output. Economists divide this period of time mainly into two parts :-

1) Short - Period or Short - Run :- Short - run is defined as that period of time in which one or more factors of Production or inputs are fixed and others are variable.

2) Long - Period or Long - Run :- Long - Period or Long - Run is defined as that period of time in which all factors of production or inputs are variable.

Returns to a Factor :- A producer may effect a change in his production by changing only the variable factor , other factors and technology remaining constant. Consequently , there is a change in the proportion of combination of factors of production. This proportional relationship between production and variable factor of production is termed as return to a factor. These , returns to a factor exhibit three phases :-

1) Increasing Returns to a Factor :- Increasing return to a factor refers to a situation in which each additional unit of the variable factor adds more to the firms output and marginal product of the variable factor rises as more of it is used.

2) Constant Returns to a Factor :- Constant returns to a factor refers to a situation in which additional units of a variable factor add the same amount to the firms output and the marginal product of the variable factor is constant.

3) Diminishing Returns to a Factor :-    Diminishing Returns to a Factor refers to a situation in which each additional unit of a variable factor adds less to the firms output , and the marginal product of the variable factor falls as more of it is used.

Fluid Mechanics - Kinematics of Flow and Ideal Flow

Kinematics is defined as that branch of science which deals with the motion of particles without considering the forces causing the motion. The velocity at any point in a flow field at any time is studied in this branch of fluid mechanics.

Types of Fluid Flow :-

1) Steady and Unsteady Flows :- Steady flow is defined as that type of flow in which the fluid characteristics like velocity , pressure , density etc. at a point do not change with time.
Unsteady Flow is that type of flow , in which the fluid characteristics like velocity , pressure , density etc. at a point change with respect to time.

2) Uniform and Non-Uniform Flow :- Uniform flow is defined as that type of flow in which the velocity at any given time does not Change with respect to time.
Non-uniform Flow is defined as that types of flow in which the velocity at any given time changes with respect to time.

3) Laminar And Turbulent Flow :- Laminar flow is defined as that types of flow in which the fluid particles move along a well-defined path or stream line and all the stream lines are straight and parallel.
Turbulent Flow is defined as that types of flow in which the fluid particles move in a zig-zag way. Due to the movement of fluid particles in a zig-zag way, the Eddies formation takes place which are responsible for high energy loss.

4) Compressible and Incompressible Flows :- Compressible flow is defined as that types of flow in which the density of a fluid changes from point to point or in other words the density is not constant for the fluid.
Incompressible flow is defined as that types of flow in which the density is constant for the fluid flow. Liquids are generally incompressible while gases are compressible.

5) Rotational and Irrotational Flows :- Rotational flow is defined as the that types of flow in which the fluid particles while flowing along a stream lines , also rotate about their own axis.
Irrotational flow is defined as that types of flow in which the fluid particles while flowing along a stream lines , but do not rotate about their own axis.

One-, Two-, and Three - Dimensional Flows :- One - dimensional is that types of flow in which the flow parameters such as velocity is a function of time and one space co-ordinate only , say x.
Two-dimensional flow is that types of flow in which the velocity is a function of time and two rectangular space co-ordinates say x and y.
Three-dimensional flow is that types of flow in which the velocity is a function of time and three mutually perpendicular directions.

- Rate of Flow and Discharge :- It is defined as the quantity of fluid flowing per second through a section of a pipe or a channel.

- Continuity Equation :- The equation based on the principle of conservation of mass is called continuity equation.  Thus for a fluid flowing through the pipe at all the cross-section , the quantity of fluid per second is constant.

Fluid Mechanics - Pressure and its Measurement in terms of fluid flow

Consider a small area dA in large mass of fluid. If the fluid is stationary, than the force exerted by surrounding fluid on the area dA will always be perpendicular to the surface dA. If the F force acting on an area dA than the pressure is defined as the force (F) per unit area is known as the intensity of pressure.

Pascal's Law :- It state that the pressure or intensity of pressure at a point in a static fluid is equal in all directions.

- Absolute Pressure :- Absolute pressure is defined as the pressure which is measured with the reference to absolute vacuum pressure.

- Gauge Pressure :- Gauge Pressure is defined as the pressure which is measured with the help of a pressure measuring instrument , in which the atmospheric pressure is taken as a datum. The atmospheric pressure on the scale is marked as a zero.

- Vacuum Pressure :- Vacuum Pressure is defined as the pressure below the atmospheric pressure.
The relationship between the absolute pressure, gauge Pressure and vacuum pressure are :-

1) Absolute Pressure = Atmospheric Pressure + Gauge Pressure

2) Vacuum Pressure = Atmospheric Pressure - Absolute Pressure

- Measurement Of Pressure :- The pressure of a fluid is measured by the following devices :-

1. Manometers :- Manometers are defined as the devices used for measuring the pressure at a point in a fluid by balancing the column of fluid by the same or another column of the fluid. They are further classified as :-

(A) Simple Manometers :- A simple manometer consist of a glass tube having a one of its end connected to a point where pressure is to be measured and other end remains open to the atmosphere. Common types of simple manometers are :

* Piezometer
* U-tube Manometer
* Single Column Manometer

(B) Differential Manometers :- Differential manometer are the devices used for measuring the difference of pressure between two points in a pipe or in two different pipe. A differential manometer consist of a U-tube , containing a heavy liquid , whose two ends are Connected to a points , whose difference of pressure is to be measured. Most commonly types of differential Manometers are :

* U-tube differential manometer
* Inverted U-tube differential manometer

2. Mechanical Gauges :- Mechanical gauges are defined as the device used for measuring the pressure by balancing the fluid column by the spring or dead weight. The commonly used mechanical pressure gauges are :

(A) Diaphragm Pressure Gauge.
(B) Bourdon tube pressure gauge.
(C) Dead - Weight pressure Gauge.
(D) Bellows pressure Gauge.

CHEMISTRY - Concept of Emission and Absorption Spectra

An instrument used to separate the radiations of different wavelengths is called Spectroscope or a spectrograph. A spectrograph consist of a prism or a diffraction grating for the dispersion of radiations and a telescope to examine the emergent radiations with the human eye. However, if in a spectroscope , the telescope is replaced by a photographic film, the instrument is called a spectrograph and the photograph of the emergent radiation recorded on the film is called a spectrogram or simply a spectrum of the given radiation. The branch of science dealing with the study of spectra is called spectroscopy.
The spectra are broadly classified into :-
1. Emission Spectra.
2. Absorption Spectra.

1. Emission Spectra :- When the radiation emitted from the some sources, e.g. from the sun or by passing electric discharge through a gas at low pressure or by heating some substances to high temperature etc. is passed directly through the prism and then received on the photographic plate, the spectrum obtained is called 'Emission spectrum'.

Depending upon the source of radiation, the emission spectra are mainly of two types :-

(A) Continuous spectra :- When white light from the any source such as sun, a bulb or any hot glowing body is analysed by passing through a prism , it is observed that it splits up into seven different wide bands of colours from violent to red, ( like rainbow ). These colours are so continuous that each of them merges into the next. Hence the spectrum is called continuous spectrum.
It may be noted that on passing through the prism , red colour with the longest wavelength is deviated least while violet colour with shortest wavelength is deviated the most.

(B) Line Spectra :- When some volatile salt is placed in the Bunsen flame or an electric discharge is passed through a gas at low pressure, light is emitted. The colour of light emitted depends upon the nature of substance. For example , sodium or its salts emit yellow light while potassium or it's gives out violet light. If this light is resolved in a spectroscope, it is found that no continuous spectrum is obtained but some isolated coloured lines are obtained on the photographic plate separated from each other by dark spaces. This spectrum is called 'Line emission spectrum' or simply Line spectrum.
Each line in the spectrum corresponds to a particular wavelength. Further, it is observed that each element gives its own characteristic spectrum, differing from those of all other elements. For example, Sodium always gives two yellow lines. Hence, the spectra of the element are described as their finger prints differing from each other like the finger prints of the human beings.

2. Absorption Spectra :- When white light from any source is first passed through the solution or vapours of a chemical substance and then analysed by the spectroscope, it is observed that some dark lines are obtained in the otherwise continuous spectrum. These dark lines are supposed to result from the fact that when white light ( Containing radiations of many wavelengths ) is passed through the chemical substance , radiations of certain wavelengths are absorbed, depending upon the nature of the element. This shows that the wavelengths absorbed were same as were emitted in the emission spectra. The spectrum thus obtained is , therefore , called 'absorption spectrum' .

Discovery of Neutron

Moseley , in 1913 , performed experiments to determine the exact quantity of charge present on the nucleus. The number of units of positive charge present on the nucleus was called the atomic number of the element. Since each unit of positive charge corresponds to one proton, therefore , atomic number was equal to the number of protons present in the nucleus. Further , since each proton has one unit mass on the atomic mass scale , therefore , the mass of the atom was calculated from the number of protons present in the nucleus (remembering that electrons have negligible mass).
Chadwick , in 1932 , performed some scattering experiments in which he bombarded some light elements like beryllium and boron with fast moving alpha - particles. He found that some new particles were emitted which carried no charge I.e. were neutral but had a mass nearly equal to that of proton. This particle was termed 'Neutron'.

Hence , the neutron may be defined as :- A neutron may be defined as that fundamental particle which carries no charge but has a mass nearly equal to that of hydrogen atom or proton.

Discovery of Proton - Study of Anode Rays

Since the atom as a whole is electrically neutral and the presence of negatively charge particles in it was established , therefore it was thought that some positively charged particles must also be present in the atom. For this purpose, Goldstein in 1886, performed discharge tube experiments in which he took perforated cathode and a gas at low pressure was kept inside the tube. 
On passing high voltage between the electrodes , it was found that some rays were coming from the side of the anode which passed through the holes in the cathode and produced green fluorescence on the opposite glass wall coated with zinc sulphide. These rays were called anode rays or canal rays or positive rays.

Origin of Anode Rays :- These rays are believed to be produced as a result of the knock out of the electrons from the gaseous atoms by the bombardment of high speed electrons of the cathode rays on them. Thus, anode Rays are not emitted from the anode but are produced in the space between the anode and the cathode.

Properties of Anode Rays :- In actual there are the same method of we discuss in cathode rays. The anode rays were found to possess the following main properties :-

1. They travel in the straight lines. However, their speed is much less than that of the cathode rays.

2. They are made up of material particles.

3. They are positively charged, as indicated by the direction of deflection of these rays in the electric and magnetic fields. That is why they are called 'positive rays' 

4. Unlike cathode rays, the ratio, charge/mass is found to be different for the particles constituting anode rays when different gases are taken inside the discharge tube. In other words, the value of charge/mass depends upon the nature of the gas taken inside the discharge tube.

5. The value of the charge on the particles constituting the anode rays is also found to be depends upon the nature of gas taken inside the discharge tube. However, the charge on these particles is found to be a whole number multiple of the charge present on the electrons. In other words , these positively charged particles may carry one, two or three units of positive charged , depending upon the number of electrons knocked out.

6. The mass of the particles constituting the anode rays is also found to be different for different gases taken in the discharge tube. However, it's value is found to be nearly equal to be that of the atom of the gas.

Hence, a proton may be defined as :- A proton may be defined as that fundamental particle which carries one unit positive charge and has a mass nearly equal to that of hydrogen atom. 

It may be mentioned here that in case of any other gas taken inside the discharge tube, the mass of the positively charged particles was found to be nearly a whole number multiple of the mass of the proton. Hence, it led to the belief that porton must be fundamental particles present in all atoms and that the atoms of gases other than hydrogen contained some whole number of protons.

Discovery of Electron - Study of Cathode Rays

The electrical nature of matter had been indicated in very early experiments on the production of frictional electricity.  This was further confirmed by the experiments on the electrolysis of substances by Davy, Stoney and Faraday in the first half of the nineteenth century. However, the discovery of electrons came as a result of the study of conduction of electricity through gases as explained :-

William Crookes, in 1879, study the conduction of electricity through gases at low pressure. For this purpose, he took a discharge tube which is a long glass tube , about 60cm long, sealed at both the ends and fitted with the two metal electrodes. It has a side tube fitted with a stop cock.
The tube is connected to a vacuum pump and the pressure inside the discharge tube is reduced to at low as 0.01 mm. Now, when a high voltage is applied between the electrodes, it is found that some invisible rays are emitted from the cathode. The presence of these rays is detected from the fact that the glass wall of the discharge tube opposite to the cathode begins to glow with a faint greenish light. Obviously, this must be due to the bombardment of the wall by some rays emitted from the cathode. These rays were cathode rays.

Properties of Cathode Rays :- From the various experiments carried out by J.J. Thomson (1897) and others, the cathode rays have been found to posses the following properties :-

1. They produce a sharp shadow of the solid object placed in their path. This shows that cathode rays travel in straight lines.

2. If a light paddle wheel mounted on the axle is placed in their path, the wheels begins to rotate. This shows that cathode rays are made up of material particles.

3. When an electric field is applied on the cathode rays , they are deflected towards the positive plate of the electric field. This shows that cathode rays carry negative charge.

4. When cathode rays strike a metal foil , the latter becomes hot. This indicates that cathode rays produce heating effect.

5. They cause ionization of the gas through which they pass.

6. They produce X-rays when they strike against the surface of hard metals like tungsten, molybdenum etc.

7. They produce green fluorescence on the glass walls of the discharge tube as well as on certain other substances such as zinc sulphide.

8. They affect the photographic plates. 

9. They possess penetrating effect. They are stopped only by metal foils of greater thickness.

Hence, the electron may be defined as :-  An electron is that fundamental particle which carries one unit negative charge and has a mass nearly equal to 1/1837 th of that of hydrogen atom.

Origin of Cathode Rays :- The cathode rays are first produce from the material of the cathode and then from the gas inside the discharge tube due to bombardment of the gas molecules by the high speed electrons emitted first from the cathode.

CHEMISTRY - Thermistors

Thermistors :- A thermistor is a heat sensitive device whose resistivity changes very rapidly with the change of temperature. The temperature co-efficient of resistivity of a thermistor is very high, which may be positive or negative.
Thermistor are usually prepared from oxides of various metals such as nickel, iron, copper, cobalt etc. These compounds are also semi-conductor. The size of thermistor is very small. The thermistors are generally in the form of beads, discs or rods. A pair of platinum leads are attached at the two ends for electric connections. This arrangement is sealed in a small glass bulb.
A thermistor can have a resistance in the range of 0.1 ohm to 10 power 7 ohm, depending upon its composition. A thermistor can be used over a wide range of temperature.
A thermistor differs from an ordinary resistance in the following ways :-
1. The temperature coefficient of resistivity of a thermistor is a very high.
2. The temperature coefficient of resistivity of a thermistor can be both positive and negative.
3. The resistance of thermistor changes very rapidly with change in temperature.

Important application of thermistor :-

1. Thermistors are used to detect small temperature changes and to measure very low temperature. A typical thermistor can be easily measure a change in temperature of 10 power -3 degree celcious

2. Thermistor are used to safe-guard the filaments of the picture tube of a television set against the variation of current.

3. Thermistor are used to temperature control units of industries.

4. Thermistors are used in the protection of windings of generators, transformers and motors.

5. Thermistors are used for voltage stabilisation and remote sensing.

Super-Conductivity :- Professor K. Onnes in 1911 discovered that certain metals and alloys at very low temperature lose their resistance considerably. This photochemical is known as super-conductivity. As the temperature decreases , the resistance of the material also decreases , but when the temperature reaches a certain critical value ( called critical temperature or transition temperature ) , the resistance of the material completely disappeares I.e it becomes zero. Then the material behaves as if it is a super-conductor and there will be flow of electrons without any resistance whatsoever. The critical temperature is different for different materials.
Super-conductivity is a very interesting field of research all over the world these days. The scientists have been working actively to prepare a room temperature super conductor and have met with some success only.

Applications of super-conductors :-

1. Super conductors are used for making very strong electromagnets

2. Super conductivity is playing an important role in material science research and high energy particles physics.

3. Super conductivity is used to produce very high speed computers.

4. Super conductors are used for the transmission of electric power.

Particulates - as Pollutants

Small solid particles and liquid droplets suspended in the air are collectively are called as particulates. Some important characterstics of these particulates are as under :-

* Size. Their size varies from 5nm to 500000 nm.
* Mass. Their mass varies from 60ug to 2000ug per cubic meter in urban and industrial areas.
* Concentration. Their number varies from few hundred per cubic cm in clear air to polluted air.
* Surface Area. They have large surface Area due to which they have good sorption for organic as well as inorganic matter.
* Chemical nature. Different types of particulates have a different chemical nature.

Sources of Particulates :-

* Natural Sources :- These include volcanic eruptions , grinding , blowing of dust and soil by the wind , spraying of salts by seas and oceans etc.

* Man-made sources :-

(A) Soot :- These are the smallest particulates. They are the most common particulates introduced in the air due to incomplete combustion of fossil fuel such as coal wood , fuel oil , natural gas etc.

(B) Fly Ash :- These are ash particles coming alongwith furnace flue gases and are the biggest particulates. They are produce due to high ash fossil fuels as in the thermal power plants or in smelting and mining processes.

(C) Inorganic particulates :- A few common inorganic particulates are :-
* Metallic particles :- These are discharging into the air during finishing of metals.
* Metal oxides :- They are released into the atmosphere during the combustion of fuels containing metals compounds.
* Lead halides :- Tetraethyl lead is added to gasoline to act as an anti - knocking agent.
* Asbestos dust :- Asbestos is a fibrous silicate mineral which is introduced in the atmosphere by the industries manufacturering asbestos sheets, ropes etc.
* Sulphuric acid and nitric acid :- These particulates in the form of droplets produce in the atmosphere when oxides of sulphur or nitrogen come in contact with the moisture.

(D) Organic Particulates :- Organic Particulates include paraffins, olefins and aromatic compounds , particularly polycyclic aromatic hydrocarbons. These originate from the combustion of static fuels or automobiles fuels or from petroleum refineries. The polycyclic hydrocarbon are easily absorbed on the soot particles and prove to be great health hazards.

Harmful effects of particulates pollutants :-

* Effect on human :- Different type of lung disease are causes by different type of particulates. e. g asbestos cause asbestosis , dust containing free silica cause silicosis etc.
Lead particulates are highly poisonous and have a serious effect on a children's brain and cause cancer.
* Effacts on Plants :- Particulates deposit on the leaves of the plants thereby blocking the stomata and retarding and transmission of mineral from the soil.

* Effects on material :- Particulates damage a large number of material e.g suit , dust , fumes , clothes , building , soil , etc. They also accelerates corrosion of metals.

* Effect on Visibility :- The light scattered by particulates result in poor visibility of the object in front of us as it happened at night when we are driving a car or scooter especially on foggy nights. They have a very harmful effects on eye retina and harmful effects on Visibility of a human beings which is a very dangerous for any one of human beings.

Effect on Climate :- Particulates act as a nuclei for cloud formation and hence effect the climate. Further , they scattered and reflected back the heat of the sunlight and controlling the warming up of the earth surface during to increase in carbon dioxide I.e. they counteract the green house effect.

Control of Particulates Pollution :- To reduced the pollution in the air , the removal of Particulates is very essential. This is done by using the following techniques which are based on the settling or washing away of the particulates.

* Gravity settling chamber :- It consist of a horizontal rectangular tank. It is so large that the effluented gases which are allowed to enter into the slow down.

* Cyclone Collector :- In this techniques, the gas is allowed to flow at tight circular spiral. Due to the centrifugal force , the particulates move towards the wall and start settling down.

* Wet Scrubbers :- In this techniques, spray towers and chamber are used into which a suitable liquid is introduced in the form of a fine spray which washes away the particulates.

* Electrostatic precipitation :- This is the most effective and efficient method for the removal of Particulates. About 99% of the particulates can be removed by this method.

Oxides of Sulphur :- as Pollutant

The two oxides of sulphur, I.e. SO2 and SO3 are the most serious pollutants of the atmosphere. Both are colourless gases with pungent smell.

Natural Source of release of sulphur dioxide into the atmosphere is the volcanic eruptions. It accounts for about 67% of the total amounts of sulphur dioxide present on the globe. The remaining 33% is discharge into the atmosphere due to human activity.

Man-Made Sources mainly include the following :-
* Combustion of sulphur containing coal and fuel oil in the thermal power plants.
* Roasting of sulphide ores in the smelting industries.
* A small amounts of sulphur dioxide undergoes photolytic oxidation in the air to form SO3.
* In the presence of water vapours, SO3 reacts to form sulphuric acid. Which remains suspended in the air as droplets or comes down in the form of acid rain.

Harmful Effects of Oxides of Sulphur :-
* SO2 and SO3 are both strongly irritating to the respiratory tract. SO2 at concentration of 5 ppm cause throat and eye irritating. It causes breathlessness and affects larynx, I.e voice box. SO3 is more harmful even at a concentration of 1 ppm and causes severe discomfort. Elderly persons and those with heart and lung disease are most seriously affected.
* Even a very low concentration of sulphur dioxide has a very damaging effects on the plants. If exposed for a Long time , a few days or weeks , it shows down the formation of chlorophyll resulting in the injury to the leaf including loss of green colour. This is called chlorosis.
* Sulphur oxides as such or after beings converted into sulphuric acid damage a number of material :

(a) They damage building material like especially marble.

(b) They corrodes metals, particularly iron and steel.

(c) They bring about fading and deterioration of fabrics leather and paper.

(d) They affect the colour of the paints.

Control of Oxides of Sulphur pollution :- The sulphur oxides pollution can be controlled in a number of ways as follows :-

* By use of low sulphur or sulphur free fuels like natural gas.

* By removing sulphur from the fuel before burning.

* By making sulphur free liquefied gaseous fuel from coal.

* By using alternate sources of energy , e.g hydroelectric power plants and nuclear plants.

* By removal of Oxides of sulphur from flue gases.

Fluid Mechanics

Fluid Mechanics :- Fluid mechanics is that branch of science which deals with the behavior of fluids at a rest as well as in motion. Fluid Mechanics is that science which study the static, kinematic and dynamic behavior of fluids.

Properties of Fluids :-

1. Density or Mass Density :- Density or mass density of a fluid is defined as the ratio of mass of a fluid to its volume . Thus the mass par units volume of a fluid is called Density or mass density. It is denoted by p (rho). It's SI units is kg per cubic meter.

2. Specific weight or weight density :- Specific weight or weight density of a fluid may be defined as a ratio of the weight of fluid to the its volume. Thus the weight per unit volume of a fluid is called specific weight or weight density. It is denoted by 'w'. It's SI unit is Newton per unit cubic meter.

3. Specific Volume :- Specific volume of a fluid is defined as the volume occupied by the volume per unit mass . Thus the volume per unit mass of a fluid is termed as specific volume. It is the reciprocal of density or mass density.

4. Specific Gravity :- Specific gravity of a fluid is defined as the ratio of density of the fluid to the density of the standard fluid. Specific gravity is a dimensionless. It is denoted by 'S'.

Viscosity :- Viscosity is defined as the properties of fluid which offers a resistance to the one layer of the fluid to the another layer of the fluid is defined as the viscosity. It is denoted by 'tau'.

Newton's law of Viscosity :- It states that the shear stress of a liquid surface is directly proportion to the rate of shear strain. The constant of proportionalty is termed as a coefficient of viscosity.

Surface Tension :- Surface tension is defined as the tensile force acting on the surface of a liquid in a contact with the gas or on the surface of miscible two liquid surface. It is denoted by sigma.

Capillarity :- Capillarity is the phenomenon of rise and fall of a liquid surface in a small tube with the adjacent general level of liquid when small tube held in a vertical position in a liquid.

Types of Fluids :-

1. Ideal Fluids :- A fluid, which is incompressible and having no viscosity . It is an imaginary fluids because all fluids have a some viscosity.

2. Real Fluids :- A fluid , which have a viscosity are termed as Real fluids. In actual all fluids are Real fluids because all fluids having some viscosity.

3. Newtonian Fluids :- A real fluid, in which shear stress is directly proportion to the rate of shear strain is termed as a Newtonian fluids.

4. Non-Newtonian Fluids :- A real fluid, in which shear stress is not directly proportional to the rate of shear strain is known as Non-Newtonian fluids.

5. Real Plastics Fluids :- A fluid , in which shear stress is more than yields value and shear stress is directly proportional to the rate of shear strain.

Bulk Modulus of Elasticity :- It is defined as the ratio of compressive stress to volumetric strain. It is denoted by 'K'.

Compressibility :- Compressibility is the reciprocal of the bulk modulus of elasticity.

Kinematic Viscosity :- It is defined as the ratio between the dynamic viscosity and density of fluid. It is denoted by the Greek symbol (v) called 'nu'.

Oxides of Nitrogen - as Pollutants

A number of oxides of nitrogen such as NO, N2O, N2O3 are introduced into the atmosphere due to natural sources and due to human activities. Out of these only two oxides , I.e NO and NO2 are considered as Pollutants. Nitric oxides is colorless and odourless gas whereas nitrogen dioxide is reddish Brown gas having pungent smell and is suffocating in nature.

Sources of oxides of nitrogen production :-
(a) Natural sources :- Natural bacterial action is the only natural source which discharges oxides of nitrogen , mainly in the form of NO, into the atmosphere in huge amounts. Besides , lightning discharge also results in the combination of N2 and O2 to form NO.

(b) Man-Made Sources :-

* Combustion of fossil fuel both in motor vehicle and stationary sources or powe plants produces so high temperature at which oxidation of the atmospheric nitrogen takes place forming NO and NO2.

The first reaction takes place at a temperature of 1200-1750*C. The reverse reaction is prevented due to rapid cooling of NO. The second reaction takes places about 1100*C.

* Chemical industries like sulphuric and nitric acid industries produce oxides of nitrogen as by - products which are discharge into the air. 

Sinks of Oxides of nitrogen pollutant :- The average residences time of NO is 4 days while that of NO2 is 3 days. During this time, they are converted into nitric acid through the reactions in which ozone plays an important role.

Harmful effects of Oxides of nitrogen pollution :-
* Neither NO nor NO2 is a health hazards at the present pollution levels. Out of the two , NO2 is more dangerous as it is a toxic gas and affects a respiratory system and damages the lungs. It's concentration at 100ppm may be fatal for animals and human beings. Though NO has about 1500 times greater affinity than CO for hemoglobin but fortunately, it is unable to enter the blood stream from the atmosphere. But it's presence in large amount may result in the increase of NO2 by oxidation and thus become harmful.
* Some sensitive Orr ornamental plants are affected by the presence of Oxides of nitrogen in the ambient air even at low concentration. Their photosynthetic activities decreases  and they start shedding their leaves and fruits.
* In the presence of Oxides of nitrogen , textiles like cotton , rayon etc. start fading.
* The acid rain causes the pH of the soil to decreased to 4 or 5 and thus reduced the fertility of the soil.
* The most serious hazards of nitrogen oxides is in the formation of an unpleasant mixture of gases and particulates that make up photochemical smog.

Control of oxides of nitrogen :-
* Just as in case of CO , the catalytic converters are used in the automobiles exhaust which is in the first stage convert the oxides of nitrogen to free N2 or to a small amount of NH3.

* The flue gases coming from the power plants or industrial units and containing NO2 and SO2 are free from these gases by scrubbing them with sulphuric acid.

Green Chemistry

One of the major cause of environmental pollution is the rapid industrilization particularly the development of those industries which either produce or use toxic chemicals. One way to protect our environment from chemical effluents and wastes is to use Green Chemistry. By green chemistry , we mean producing the chemicals of our daily needs using such reactions and chemical processes which neither use toxic chemicals nor emit such chemicals into the atmosphere. Although it is a challenging task but some initial efforts have already been made to acheive this goal.

Techniques Used :- Green Chemistry does not employ toxic reagent or solvents and severe conditiin but use mild and environmental friendly reagent such as sunlight , microwaves , sound waves , and enzymes. Each of these is briefly described below :-

1. Use of sun light and microwaves :- The use of sunlight and ultraviolet light have given birth to photochemistry. During the past forty years, a number of photochemical reactions have been studied and their condition standardized. One major advantage of these reaction is that sometimes the prroduct of photochemical reactions are such that they cannot obtained by usual chemical method. Recently, many known reaction have also been carried out using microwave ovens. In these reaction , no toxic solvent are used but only the reactant in proper ratio are mixed on a solid support such a alumina and exposed to microwaves. The reaction is complete with in minutes and yields are not only comparable but in some cases, they are even higher than those obtained under serve conditions using toxic solvents. Thus the uses of microwave have not only reduced the time of reaction but have also increased the yields. Efforts are , however, needed to develop the solid support and optimization the dose of microwave radiation to realise the desired results.

2. Use of Sound Waves :- Instead of microwaves , sound wave have also been used to carry out certain known chemical reaction with encouraging results. This branch of chemistry is called sonochemistry. Here again efforts are needed to developed conditions to achieve the desired goals.

3. Use Of Enzymes :- One of the most throughly investigated environmental friendly reagents are enzymes. These work in aqueous solution and at ambient temperature. Using these enzymes many biochemical method have been developed to prepare precursors and intermediates of certain medicine and antibiotics.

Green Chemistry in Day-to-Day Life :- A few examples are of the chemical used/produced and the techniques employed in green chemistry are given below :-

1. Dry cleaning of clothes and laoundary :- Earlier tetrachloroethene was used as solvent for dry cleaning. This compound is suspected to be carcinogenic and contaminated the ground water. It's use has been replaced by liquefied carbon dioxide along with a suitable detergent which is less harmful. Similarly, for bleaching of clothes in the laundary, hydrogen peroxide is beings used which gives better results and is not harmful. Moreover, it saves as a lot of water.

2. Bleaching of paper :- Earlier , chlorine gas was used for bleaching paper which is highly toxic chemical. It's use has been replaced by hydrogen peroxide along with a suitable catalyst.

3. In synthesis of chemicals :- For examples ,  ethanal is now-a-days being prepared on a commercial scale using environment - friendly chemical and conditions. The yields is about 90% .

From the above discussion , it is evident that if concerted efforts are made to develop green chemical products, it will certainly help us to keep our environment pollution free.

CHEMISTRY - Troposphere Pollution

The five major pollutants present in the air :-

1. Carbon monoxide
2. Hydrocarbon
3. Oxides of nitrogen
4. Oxides of sulphur
5. Particulates

Now, we shall discuss the sources, harmful effect and the method to control each of these pollutant. It is colourless, odourless and tasteless gas. It is 96.5% as heavy as air.

* Sources of Carbon monoxide production :-

(a) Due to human activity :-   

*  Incomplete combustion of fossil fuels or hydrocarbon fuels in the automobiles.
* Forest fires or agricultural wastes burning.
* Reaction of carbon dioxide with carbon containing material at high temperature.

(b) Natural sources :-
* From conversion of methane produced by the bacterial decay ogre living or organic matter (80%).
* From synthesis and decay of chlorophyll (3%).
* From oceans and other undetermined sources (10%).

Harmful Effect of Carbon monoxide :- carbon monoxide is poisonous because it combines with hemoglobin of the red blood corpuscles about a 200 times more easily than does oxygen to form carboxyhemoglobin reversibly as follows :-
                Hb. + CO - HbCO
The normal function of the hemoglobin is to combines with Oxygen in the lungs to form hemoglobin.
The oxyhemoglobin travels to the different body cells where it gives up oxygen and takes up carbon dioxide for returns to the lungs which is then exhaled out. However, if large amounts of carbon monoxide is present in the surrounding air, it combines more readily with the hemoglobin. Thus, transport of oxygen to the differents parts of the body is inhibited. In other words, the body becomes oxygen-starved.

Control of Carbon monoxide pollution :- The main source of CO pollution due to human activities is the use of internal combustion engine in the automobiles. These engine emit a mixture of CO , Oxides of nitrogen and particulates. However, any method used to control any one of these pollutants result in the increase in the other pollutants. A few method of controlling a CO Pollution are as follows :-
* The carbarettor is adjusted so as to give a proper air fuel ratio.
* The exhaust system is developed in such a way that it brings about complete combustion in the fuel so that negligible CO is formed.
* Catalytic converters can be fitted into the exhaust pipe which may convert the poisonous gases like CO into harmless products before they are thrown into the air.
* Modifications of internal combustion engine have been done by certain companies like Honda and Toyota of Japan instead of catalytic converters.
* Instead of gasoline , the use of CNG ( Condensed Natural gas ) and LNG ( Liquefied natural gas ) has been started as they are pollution free fuels.

2. Hydrocarbons as pollutants :- Many differents hydrocarbons are present in the air. Most of these hydrocarbons are of low molecular mass and are gases or volatile liquids at ordinary temperature. Methane the simplest hydrocarbons is the most abundant hydrocarbon carbon pollutant. In Los Angeles ( in USA ) where the vehicular traffics is very high , its amounts in the air was found to be 3ppm in 1965.

Sources of Hydrocarbons :-
(a) Natural Sources :-
* Trees emit large amounts of hydrocarbons in the air.
* Methane is released into the air in large quantities by the anaerobic decomposition of organic matter in soil, water and sediments.
* Domestic animals contributed a very huge amount of methane into the air every years.

(b) Man-Made sources :-
* Just as in case of CO , the largest man-made source of hydrocarbons pollutant is the internal combustion engine. About a 15% of the total hydrocarbons present in the air is from this source.
* Some hydrocarbon pollution also takes places due to burning of stationary fuel , I.e coal , wood, kerosene oil etc.
* Evaporation or organic solvent like benzene, toluene etc. during industrial operations add sub- stantially to the total hydrocarbon pollution.

Harmful Effects of Hydrocarbon Pollution :-
* At low concentrations, as they exist in through air at present, there are no harmful effects of the hydrocarbon on human beings. However , if their concentration rises to 500-1000 ppm, they have carcinogenic effect on the lungs and cause cancer.
* Due to their photochemical reactions with oxygen and oxides of nitrogen , they form photochemical oxidants and photochemical smog which have a strong damaging effect on the human beings as well as plants.

Control of Hydrocarbon Pollution :- As automobiles are the main sources of hydrocarbon pollution, all those steps taken to control CO pollution are needed for controlling hydrocarbon pollution. 

3. Oxides of Nitrogen .

4. Oxides of Sulphur .

5. Particulates .

ORGANIC CHEMISTRY - Resonance

The phenomenon of resonance is said to occur if for a molecule, we can write two or more than two Lewis structures which differ in the position of electrons and not in the relative position of atoms. The various Lewis structures are called canonical structures or the resonance structures. The real structure of the molecule is not represented by any one of the canonical structures but is a resonance hybrid of the various resonance structures. The various resonance structures are separated by a double headed arrow. This arrow should be clearly distinguished from that used for an equilibrium.
Resonance hybrid is always more stable than any of its canonical structures. Thus, the actual molecule of benzene is more stable than either of two Kekule structures. The magnitude of stability conferred for a molecule as a result of resonance is expressed in terms of resonance energy or delocalization energy. It is defined as the difference in internal energy of the resonance hybrid and that of the most stable canonical form.

Heat of hydrogenation :- Heat of hydrogenation is the amounts of heat evolved when one mole of an unsaturated compound is hydrogenrated.

Halogenation :- The halogenation of benzene and some others arenes is carried out at low temperatures, in the absence of sun light and in presence of Lewis acid such as anhydrous ferric or aluminium chloride as catalyst.

CHEMISTRY - Organic Compound

The simplest organic compounds containing only carbon and hydrogen are called hydrocarbons. They are considered to be parent organic compounds while all the organic compounds are thought to have been derived from them by replacement of one or more of their hydrogen atoms by other atoms or group's of atoms. As the study of ore chemistry advanced, the number of organic compounds became very large. As a result, it became rather inconvenient to study the chemical behavior of these compounds individually. Therefore, in order to simplify the systematize the study of organic chemistry, all the known organic compounds have been broadly divided into two categories depending upon the nature of their carbon skeleton. These are :-

1. Acyclic or open chain compounds.
2. Cyclic or closed chain compounds.

1. Acyclic or Open chain compounds :- These compounds contain open chains of carbon atoms in there molecules. The carbon chains may be either straight chains or branched chains.
Open chain compounds are also called alphabetic compounds since the earlier compounds of this class were obtain either from animal or vegetable fats.

2. Cyclic or closed chain or ring compounds :- These compounds contain one or more closed chain or rings of atoms in their molecules. Depending upon the constitution of the ring, these are further divided into the following two categories :-

* Homocyclic or Carbocyclic compounds :- These compounds contain rings which are made up of only one kind of atoms, I.e carbon atoms. These are further divided into the following two sub-classes.

(a) Acyclic compounds :- Carbocyclic compounds which are resemble alphabetic compounds in most of their properties are called alicyclic compounds.

(b) Aromatic compounds :- These are special type of cyclic unsaturated compounds. The name aromatic for this class of cyclic unsaturated compounds has been derived from the Greek word aroma meaning fragrant smell simple since most of the compounds discovered earlier had pleasant smell.

* Heterocyclic Compounds :- Cyclic compounds containing one or more heteroatoms in their ring are called heterocyclic compounds.
The heteroatoms commonly found in these compounds are oxygen , nitrogen and sulphur but occasionally phosphorus, boron, silicon and some metal atoms like tin, selenium etc. may also be present. Depending upon the chemical behavior , they are further classified into the following two categories :-

(a) Alicyclic Heterocyclic Compounds :-  Aliphatic cyclic compounds containing one or more heteroatoms in their ring are called alicyclic heterocyclic compounds.

(b) Aromatic heterocyclic compounds :- Aromatic cyclic compounds containing one or more heteroatoms in their molecule are called aromatic heterocyclic compounds.

Green House Effect and Global Warming

Carbon dioxide present in normal concentration in the air is not an air pollutant. Rather it helps to maintain the temperature on the earth required for the existence of living organisms. However, due to human activities such as burning of fossil fuel like coal, natural gas, petroleum etc. The amount of carbon dioxide in the air is increasing. This result in warming of the earth surface and thus bring about drastic changes in the climate as explained below :-

Out of sun's energy entering the atmosphere about 34% is scattered and reflected back by the particulates and the remaining 66% is absorbed by the earth. The reason for this energy reaching the earth is that visible and ultraviolet radiation can pass through carbon dioxide and water vapour present in the atmosphere. Ultraviolet radiation are absorbed by ozone layer but visible light reaches the earth and heats it up. However, when the earth cools, the energy is 're-emitted from the earth surface in the form of infrared radiations. These radiation can be absorbed by carbon dioxide and water vapours but cannot pass through them. The heats thus absorbed by carbon dioxide and water vapours cannot go to the upper atmosphere and is radiated back to the surface of the earth. In this way, additional heat is kept with in the lower atmosphere and warming of the earth occurs.
The phenomenon has been named as green house effect because it is similar to a green house for plants. A green house is a place where plants are grown on the soil but there are walls and roof made of glass. The sun's energy can enter through the glass but cannot go out of it. The energy is thus absorbed by the soil and the structure of green house. The energy thus absorbed is 're-emitted back into the green house. The same situation is observed inside a car which becomes very hot inside when it is parked in the sun for some time with its glass windows closed. In the atmosphere, carbon dioxide is playing the role of a glass of a green house. Hence it is called green house effect.

Greenhouse Effects :-

* If the rate at which solar radiation are arriving the earth remains constant but the amount of carbon dioxide in the air increases, the heat radiated back to the earth will increase. Consequently, the temperature of the earth surface will increase. As a result, evaporation of surface water will increase which will further helps in the rise of temperature. This increase in temperature will have a drastic effect on the climate and may prove even disastrous.

* Due to higher concentration of carbon dioxide in atmosphere, the plants undergoing photosynthesis will take up the gases at a faster speed. As a result, the plants in warmer climates and adequate rainfall would grow faster.

* Higher global temperature is likely to increase the incidence of infectious disease like malaria, dengue, yellow fever and sleeping sickness.

It is important to mention that earth is being saved from excessive heating due to certain opposing factors taking place simultaneously.

How to reduce rate of global warming :- As green house gases are added into the atmosphere due to burning of fossil fuel and cutting down of forest and trees , we can follow some simple method so that the green house gases are added into the atmosphere as minimum as possible. A few of these can follow s :-

* By preferring walking or using bicycles or going for car pools or taking public transport.

* By planting a new trees every month and increasing green cover.

* By avoiding burning of dry leaves etc.

* By not smoking and persuading others also not to smoke in public places.

* By importanting knowledge to those who do not know about the greenhouse effect.

Economics and Managements

<b>Industrial Economics :-</b>Industrial economics is that branch of microeconomics which studies the economics problem of the firms and industries and the  industrial relationship with the society as whole. In the words of P. R. Ferguson and G. J. Ferguson , "Industrial economics is best defined as the application of microeconomics theory to the analysis of firms, market and industries".

<b> Microeconomics :-</b>Microeconomics is that branch of economics which studies the decision of individual households, firms and Industries.

<b>Production Function :-</b>Production function expresses the physical or technical relationship between the quantity of a good produced and the factor of production necessary to produce it. Or Production function expresses the physical or technical relationship between the output and input in a process of production.
Production function can be expressed in the form of the following mathematical formula :-
               Y = f ( L, K, S )
It will be read as : Production (Y) is the function (f) of labour (L) , Capital (K) , and Land (S).

According to Watson, "The relation between a firms physical production and the material factors of production is referred to as production function."

CHEMISTRY - Soil Pollution

Soil is the uppermost part of the earth crust and is believe to have been formed as a result of decomposition and disintegration of surface rocks due to weathering over a very long period of time. It might have been formed at far of distance but is carried by strong winds rivers to different places.
The prosperity of a nation depends upon the quality of soil as it is the soil which provides nutrients, water and minerals for the growth of the plants. It is, infact, the heart of biosphere.
However, large scale of cutting of trees for human needs due to increase in population, digging of minerals, increasing brick-kilns, poisonous effluent of the industries and dumping of toxic and harmful wastes, increase in the use of automobiles etc. are damaging the quality of the soil and resulting into soil pollution. In India, it is sad to point out that backwardness of our people is an additional factor for soil pollution, e.g using open air lavatories by slum dwellers thereby inviting pig, crows, other vulture and files, throwing of domestic wastes including peeling of vegetables and fruits, plastics, polythene bags etc.

<b>Composition of the Soil :-</b>

1. Mineral matter :- it comprise of mineral particles of different sizes which originate from the rock and are formed by its disintegration. They are present as gravel, coarse sand, fine sand, slit, and clay.

2. Organic matter :- This is present in the soil as a result of fallen trees and mixing their parts such as roots, leaves etc. And also from the remains of dead animals and their excreta. These materials are decomposed by microorganisms present in the soil and convert them into humus. Humus has all those excellent properties which are an urgent need of the plants.

3. Biological system :- It consist of algae, bacteria, protozoa etc. Which help in the decomposition of organic matter present in the soil.

4. Soil water :- The water present in  the soil acts as a solvent for various organic and inorganic materials needed for the plants and also act as a transporting agent by carrying nutrients from the soil to different parts of the plant.

5. Soil air :- It is present in the pores of the soil, i.e the space between the soil particles. It contains more of carbondioxide and moisture than oxygen. Out ids needed for soil microorganisms and underground parts of the plants.
The soil containing almost equal amounts of sand, slit and clay alongwith humus and 34% air and 66% water is consider to the best soil for most of the crops. It is called loam soil.

<b> Sources of Soil Pollution :-</b>

1. Industrial Wastes :- It has been estimated that about a 50% of the raw material used by most of the industries becomes waste product which is either thrown into the soil nearby. This industrial waste contain huge amounts of toxic and disastrous chemical many of which are non-biodegradable. Some of the industries responsible for soil pollution are paper mills , pulp mills, sugar mills, chemical industries and petroleum industry etc.

2.Urban Wastes :- Urban wastes consist of soil refuse containing garbage and rubbish material like paper pieces, glass, plastics, used cans, leaves, polythene bags, peeling of vegetables and fruits etc. These wastes emit out poisonous gases, toxic hydrocarbons and pathogenic microbes which cause disease.

3. Agricultural pollutants :- No Doubt, the use of fertilizers, pesticides , soil conditioners , etc. have increase the yield from the crops but they have polluted the soil. Their entry into food chain has adversely affected the health of the human beings and led to a number of diseases. Some of the agricultural pollutants are :-
* Fertilizers
* Pesticides
* Insecticides
* Fungicides
* Soil conditioners
* Farm wastes

4. Radioactive Pollutants :- Dumping of the nuclear wastes from the nuclear power plants into the soil has been one of the greatest source of radioactive pollution of the soil. Nuclear tests produce nuclear dust in the atmosphere which ultimately falls into soil and pollutes it. The use of atomic and hydrogen bomb in the wars produces radioactive nuclides as the by-products.

CHEMISTRY - Water Pollution

Water is one of the basic needs of household, agriculture and industry. For most of the purposes, e.g. drinking, washing etc. We need pure and clean water. However, the natural water gets contaiminated or polluted in the following two ways :-

1. By natural processes
2. By human activity

Qater pollution is defined as the contamination of water by foreign substances which make it harmful for health of animals or plants or aquatic life and make it unfit for domestic, industrial and agricultural use.
Polluted water has any one or more of the following signs :-
* It has a bad taste to drink.
* It has an offensive odour.
* It has unpleasant colour.
* It has unchecked growth of weeds.
* It may have oil or grease floating on the surface.

Types of Water Pollution :-  Based on the sources and storage of water, water pollution may be classified into five main categories as follows :-

1. Ground Water Pollution :- Water below the surface of the earth is called ground water. Most of the water is present as ground water. The remaining presents in lakes, river, streams etc. Only about 2% is present as soil moisture above the water table which is needed for the growth of plants. Ground water collects below the surface of the earth afterpassing throughthe pores of the earthly material which act as a filter for it and is pure. It is for this reason that well water or spring water is used for domestic purposes in rural areas. However, due to disposal of domastic wastes and industrial effluent and use of fertilizers and pesticides in agriculture, a number of harmful soluble substance dissolve into the rain water and pass through tbe soil and enter into ground water and result in pollution, especially where the water table is high.

2. Surface Water Pollution :- Water present on the surface of the earth in any form is called surface water. As it is an in direct contact with the atmospheric gases, a number of gases like corbon dioxide, sulphur dioxide etc. Present in the air as pollutants dissolve into it , thereby polluting it. In addition to these atmospheric gases, the surface water also gets polluted by industrial and municipal wastes, agriculture wastes including decomposed plant and animal matter and by radioactive materials.

3. Lake Water Pollution :- Lakes cover a large part of the water area . The water in them gets contaminated in a number of way as followings :-
* Organic wastes from hills and toxic effluent from urban areas flow into them.
* Industrial effluents are thrown into them.
* Sewage treatments plants discharge toxic organic matter into them.
* Dumping of huge amounts of sediments i.e. siltation of lakes.
* Inorganic nutrients from agricultural land due to surface run-off.

4. River Water Pollution :- There are 13 major rivers in India flowing through differents states. These include Ganga, Yamuna, Narmada, Brahamputra, Krishna, Cauvery, Damodar, Godavri, Hooghly, Tapti, Gomti, Sona and Chambal besides many others. There was time when the water in these rivers was very pure and clean. Ganga jal was considered to be so pure that it could be

CHEMISTRY - Air Pollution

An addition of undesirable materials into the atmosphere either due to the natural phenomena or due to the human activity on the earth which adversely affect the quality of the air and hence affect the life on the earth. This phenomenon is known as Air pollution.
When we talk about an air pollution, we mean the pollution of air upto a height of about 50 km above the surface of the earth. This part of the air is called homosphere because the different constituents present in it form a homogeneous mixture.
The composition of pure dry air is as follows :-
Nitrogen - 78.10% , Oxygen - 20.95% , Ar. - 0.93% , Corbondioxide - 0.032%
Air has never been pure right from the day the man started burning fuel. The oxides of corbon, nitrogen, and sulphur become pollutants if their amount exceeds a certain limit ( called Tolerance Limit )

<b> Sources of Air Pollution :-</b> The main sources of air pollution may be classified into two categories as follows :-
1. Natural Sources :- Thesources which occur due to natural process. Few example are :-
* Volcanic eruption emitting poisonous gases like CO , Sulphur dioxide etc.
* Forest fires and coal-refuse fires.
* Vegetatiin decay.
* Pollen grains of flowers.

2. Sources due to human activity :- These sources occur due to the human activity is known as Sources due to human activity. Few examples are :-

* Burning Of Fossil Fuels :- Which produce some poisonous gases as by - products such as CO, oxides of nitrogen etc.
* Combustion of gasoline in the automobiles:- e.g. cars, scooter, bus, trucks etc. They emit out poisonous gases like CO, oxides of nitrogen etc.
* Increase in population :- This is one of the major cause of pollution. More, the population, more are the needs, greater are the unnatural method adopted which disturb the balance or equilibirium of the atmosphere.
* Deforestation :- Man has been cuttin trees indiscriminantely to meet his needs. This has resulted in increase in the precentage of carbon dioxide and decrease in the precentage of oxygen in the air.
* Agricultural Activities :- The pesticides added to the soil or the sprays done over the crops are carried by the wind to different parts of the town where they give a foul smell and affect the health of animals and human beings.
* Wars :- The nuclear weapons used during wars emit out radiations which adversely affect the health and prove to be fatal.
* Fast Industrialisation :- In the last few years, the number of industries in different parts of the world and their production has increased manifold. These include paper mills, sugar mills, rubber and plastic industries.

<b>Effects of Air Pollution :-</b>
* Effects on Plants.
* Effects on Materials.
* Effects on Climate.
* Effects on Human Beings.