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Scheme throughout West Bengal. Nodal Agency Labour Department, Government of West Bengal will be the Nodal Agency for the Scheme. Directorate of Employment shall function as the implementing and monitoring agency under the Scheme.
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- 1 THE RAMANS BOOKSSOLAR SYSTEM - STATISTICSThe solar system consists of the Sun and 9 planetsrevolving around it in different orbits. The statistics ofthe sun and the planets are given below :SUNAge : About 5 Billion yearsDistance : 149.8 Million KmsDiameter : 1,38,400 Kms.Photosphere temperature : 5,770 KCore temperature : 150,000,000 KAbsolute visual magnitude : 4.75Rotation (as seen from theearth at the equator) : 25.38 daysRotation (near the poles) : 33 daysThe sun consists of 71% of Hydrogen, 26.5% Helium and2.5% of other elements.The rays of the Sun take about 8 minutes to reach theearth.PLANETS(1) MERCURY : It is the planet nearest tothe earth.Average distanceto the Sun : 57.6 Million Kms.Diameter : 4,849.6 Kms.Period of revolution : 88 daysPeriod of rotation : 58 days 15 hrs 30 mts. 34sec.(2) VENUS : It is also known as theMorning Star or theEvening Star. It is thebrightest of all theplanets.Diameter : 12,032 Kms.Period of revolution : 225 daysPeriod of rotation : 243 days 14mts.(3) EARTHEquatorial diameter : 12,756 Kms.Polar diameter : 12,714 Kms.Distance from the Sun : 149,597,900 Kms.Period of revolution : 365 days 5 hrs, 48 mts,45.51 sec.Period of rotation : 23 hrs 56 mts. 4.09 sec.LATEST STUDY MATERIALS WITH KEY POINTSGENERAL KNOWLEDGE(4) MARSDiameter : 6,755.2 Kms.Distance from the Sun : 225.6 Million Kms.Period of revolution : 687 daysPeriod of rotation : 24 hrs 37 mts. 22.663 sec.(5) JUPITER : This is the largest planetin the solar system.Diameter : 141,968 Kms.Distance from the Sun : 772.8 Million Kms.Period of revolution : 11.9 yearsPeriod of rotation : 9 hrs 50 mts. 30 sec.(6) SATURN : It was discovered byGalileo.Diameter : 119,296 Kms.Distance from the Sun : 1,417.6 Million Kms.Period of revolution : 29.5 yearsPeriod of rotation : 10 hrs 14 mts.(7) URANUSDiameter : 52,096 Kms.Distance from the Sun : 2,852.8 Million Kms.Period of revolution : 84 yearsPeriod of rotation : 16 hrs 10 mts.(8) NEPTUNEDiameter : 49,000 Kms.Distance from the Sun : 4,497 Million Kms.Period of revolution : 165 yearsPeriod of rotation : 18 hrs 26 mts.(9) PLUTO : This is the coldest andsmallest of all planets. Itis also the most distantone.Diameter : 3,040 Kms.Distance from the Sun : 5,865.6 Million Kms.Period of revolution : 248 yearsPeriod of rotation : 6 days 9 hrs and 18 mts.MOON : Moon is earth's satellite.Its period of rotation andPeriod of Revolution arethe same. i.e.2912 days.THE UNIVERSE
- 2 THE RAMANS BOOKSTHE EARTH DATASurface Area : 510,100,500 Sq.Kms.Land Surface : 148,950,800 Sq.Kms.(29.08%)Water Surface : 361,149,700 Sq.Kms.(70.92%)Equatorial circumference : 40,075 Kms.Polar circumference : 40,008 KmsEquatorial radius : 6,377 Kms.Equatorial Diameter : 1,22,756 Kms.Polar radius : 6,357 Kms.Polar Diameter : 12,714 Kms.Mean distance from theSun : 14,95,97,900 Kms.Period of revolution : 365 days 5 hours 48 mts.45.51 Sec.Period of rotation : 23 hrs. 56 mts. 4.091 Sec.Escape Velocity fromthe earth : 11 Km per Sec. (minimum)THE WORLDThe seasons are due to the change of the Earthsposition in the course of its revolution about the Sun,and to the inclination of its axis. The Equator is animaginary line drawn round the Earth midway betweenthe Poles. There are two other lines, namely, Tropic ofCancer (23O N) and the Tropic of Capricon (23O S).The word tropic means, turning place. The inclinationof the Earths axis together with its revolution round theSun is the cause of the varying length of day and night indifferent parts of the world. On March 21 (Vernal Equinox)and September 23 (Autumnal Equinox) the Sun is over-head at the Equator. On these dates, except at the Poles,(a) days and nights are equal all over the world; and (b)the Sun rises exactly due east and set exactly due west atall places on the Earths surface. At the Equator itselfdays and nights are equal throughout the year. BetweenMarch 21 and September 23, when the North Pole is tiltedtowards the Sun, the days are longer than the nightsthroughout the Northern Hemisphere and there iscontinuous daylight at the North Pole. Similar conditionsare experienced in the Southern Hemisphere and theSouth Pole between September 25 and March 21.Latitude and Longitude:Latitude is distance, measured in degrees, north orsouth of the Equator. Longitude is distance, measured indegrees, east or west of any fixed meridian. The meridianpassing through Greenwich is numbered 0O. On a globethe meridians are numbered from 0O to 180O E (East) or W(West). At the equator the degrees are 69 to 70 milesapart (25000360). Since earth completes one rotation onits axis in 24 hours, 360 meridians pass under the Sun inthat time. Therefore, 1 degree passes under the Sun every4 minutes.International Date Line:If we travelled westward to a place X on longitude180o W, the time there would be 12 hours behindGreenwich time (180 x 4 minutes = 720 minutes = 12 hours).If we journeyed eastward to a place Y on longitude 180oE, the time there would be 12 hours ahead of Greenwichtime. Thus X and Y both on 180o have the same time butThe Earth and the Solar System :The Earth is a member of the Solar System. It is oneof nine major planets revolving round the Sun. Of these,Mercury and Venus are nearer, and Mars, Jupiter, Saturn,Uranus, Neptune and Pluto are farther away from theSun than the Earth.The planets radiate no light of their own, but shinewith that reflected from the Sun. The Sun has a diameterof 864,000 miles (1,390,000 Kms) and it is 93,000,000 miles(150,000,000 Kms) from the Earth. The Sun is a star. Thestars, unlike the planets, are self-luminous bodies. Theother stars appear small because they are so far away;the nearest star, Proxima Centauri, is 200,000 times moredistant from us than the Sun.The Moon is a dead planet. It is about 240,000 miles(386,000 Kms) from the Earth. The Moon revolves roundthe Earth taking approximately 29 days to complete oneround. The phases of the Moon are the result of itsposition in relation to the Earth and the Sun.The Moons orbit is ecliptical and inclined at anangle of 5o to the plane of the Earths orbit. This explainswhy we do not have a total eclipse of the Sun every timethere is a new moon.The Earth:The Earth is a sphere but it is not a perfect sphere.It is slightly flattened at the poles and bulges at theequator. The circumference of the earth is approximately25,000 miles (40,000 Kms).It rotates on its axis once in every 24 hours, spinningfrom west to east. Besides spinning on its axis, it alsomoves round the Sun, called the revolution.Its orbit round the Sun is oval or ecliptical. Thetime taken to complete one revolution is approximately365 days or one year. For convenience, one year istaken as 365 days and the shortfall of day eachyear is made good in the Leap Year which consists of366 days. The Earths axis inclined to the plane of itsorbit at an angle of 66O.
- 3 THE RAMANS BOOKSdiffer in date by a day (12 hours + 12 hours = 24 hours).To overcome the confusion that would otherwise arise,the International Date Line has been established. It runsalong 180o E or W. Westward-bound vessels crossingthe Date Line drop a day from the calendar, while thosegoing eastward add a day by giving the same date to twoconsecutive days. Instead of changing the time exactlyaccording to change in degrees at the rate of 4 minutesper degree, certain time zones have been established. Allplaces in the same area or time zone or time belt, usewhat is called Standard Time. Thus we have theGreenwich Mean Time (G.M.T) and the Indian StandardTime (I.S.T). There are five time-belts in Canada and fourin United States.The Lithosphere:The mass of the Earth is generally divided into threelayers, namely, Crust, Mantle and Core. The Lithosphereis the name given to the outer Crust which is not morethan 10 miles thick. It is made up of a great variety ofrocks, soils, etc.Rocks:1. Sedimentary Rocks:These rocks are made up ofdeposits laid down on the floor of river beds, lakesand seas.Examples:Sand and sandstone, clay, lime stone,chalk and carbonaceous rocks, such as lignite, coaland anthracite.2. Igneous Rocks:These are primary rocks which areformed by cooling and solidification of molten lava.When such rocks are poured out on the surfacethey are known as Volcanic rocks, e.g. basalt. Whenthe molten material solidifies at considerable depth,plutonic rocks are formed, e.g. granite.3. Metamorphic Rocks:These rocks are formed as aresult of alteration by extreme heat and or pressureof igneous or sedimentary rocks. Example, slate,gneiss, schist etc.Soil:The upper layers of rocks weather to form the soil.There are three distinct layers of soil. The uppermostlayer forms the top soil. The second layer is called thesubsoil. The third layer is made up of decomposing andmuch-broken rock, known as mantle- rock. The type ofsoil depends on a number of factors, namely, climaticconditions, the nature of the parent rock, relief, vegetationand the period over which it has been worked by man.Soils may by broadly classified as (a) Forest, (b) Grasslandand (c) Desert types.Mountains:In past geological ages disturbances in the Earthsinterior have caused crumpling and cracking of the crust.This has resulted in great upholds forming Fold-Mountains which are mainly made up of folded strata ofsedimentary rocks, e.g. the Alps, the Rockies, the Andes,and the Himalayas. The mountain structures worn downby prolonged denudation are known as ResidualMountains, e.g. Highlands of Scotland and Scandinavia.Denudation:The process known as denudation or the wearingaway of the land is continually going on. The chief causesof such erosion are (a) changes in temperature; (b) frost;(c) winds; (d) water, including rivers; (e) ice; and (f) theaction of the sea. Steps to combat soil erosion include (i)terracing; (ii) contour ploughing; (iii) strip cropping (iv)planting shelter belts of trees; and (v) plugging the gulliesby building small dams etc.The Atmosphere:The air is composed mainly of nitrogen (78%) andoxygen (21%) with small proportions of carbon dioxide,water vapour and rarer gases like argon and neon.Atmosphere is 200 miles thick, but nine-tenths of the aircomposing it is found within 12 miles, and half within 3miles of the earths surface. We are concerned mainlywith the lower layer of troposphere. The upper layers inthe ascending order are Stratosphere, Mesosphere andIonosphere. Troposphere extends to a distance of aboutten kilometres. Stratosphere is a region extending froman altitude of about 11 Km to 50 Km above the earth. Theupper part of stratosphere has plenty of ozone whichprotects us from the fatal effects of Suns ultravioletradiation. Mesosphere is the next layer extending from 50to 80 Kms above the earth. It is a very cold region.Ionosphere extends from about 60 Kms upwards. Itincludes Thermosphere and Exosphere which marks theouter limits of the earths atmosphere.Wind is air in motion:The chief cause of wind is difference in atmospherepressure. One of the main reasons for differences inpressure is unequal heating of the air. From the highpressure belts the air flows outwards to the regions oflow pressure. Owing to the rotation of the earth, the windsdo not blow due north and south, but are deflected. Inthis deflection they obey Ferrels Law which states, Anymoving body on the earth surface including a current ofair, tends to be deflected, the deflection being to the rightin the northern hemisphere and to the left in southernhemisphere. Land and seabreezed are local winds causedby the unequal heating of land and water. During the daythe land becomes very much hotter than the sea, with theresult that there is marked low pressure over the land.Thus the air over the sea flows rapidly loses heat, but thesea remains warm for a longer time. Thus at night, heavycool air blows from the land to take the place of warm airrising over the sea. The monsoon or seasonal winds maybe regarded as land and sea breezes on a large scale, inwhich the time-frame is a year instead of a day. Thisphenomenon is to be found in south-east Asia, but isespecially marked in the subcontinent of India. A cycloneis a portion of the atmosphere in which the pressure islowest in the centre. The winds blow inwards in anti-clockwise direction in the Northern Hemisphere. In the
- 4 THE RAMANS BOOKSSouthern Hemisphere cyclonic winds blow in a clockwisedirection in accordance with Ferrels Law. An anticycloneis a portion of the atmosphere in which the pressure ishighest in the centre. The winds blow outwards in aclockwise direction in the Northern Hemisphere and inan anti-clockwise direction in the Southern Hemisphere.The Oceans:It is estimated that 72% of the surface of the globeis covered with water. The Pacific, which is the greatestof all oceans, covers a third of the earths surface, itstotal area being greater than that of all the dry land.Atlantic is slightly less than half the size of the Pacific,yet so many great rivers flow into it that it receives halfthe drainage of the world. The other oceans are Indian,Mediterranean, Antarctic and Arctic. The average depthof the ocean is 12,500 feet, compared with the averageheight of the land which is about 2,500 feet. The greatestknown depth is that of the Marianas Trench in the Pacific,where a depth of 35,800 feet has been recorded.Tides:Tides are caused by the gravitational attraction -the pull of the moon on the earth, sometimes assistedby and sometimes hindered by the Sun.At new and fullmoon, when the Sun, Moon and Earth are practically in astraight line the attractive force of the Sun increases thatof the Moon. Such high tides are called spring tides.Weather and Climates:Weather may be defined as the condition of theatmosphere at any place at a particular time. The averageweather conditions determine the climate. Humidity,temperature, elevation, distance from the sea, oceancurrents, atmosphere pressure and prevailing windscombine to affect the climate of a region.Humidity:Humidity, the term used to express the dampnessof the atmosphere, is due to the pressure of water vapour.Evaporation is the mean by which water is drawn off asinvisible water vapour from oceans, lakes, rivers, etc.,when the air contains as much water vapour as it canhold is said to be saturated. When saturated air is cooled,condensation takes place and some of the water whichform the clouds grow larger, they precipitate i.e., fall tothe earth as rain. The proportion of water vapour in theair, compared with the maximum it can hold at the sametemperature, is known as Relative Humidity. Dew iscaused by the condensation of water vapour on the coldground during the night. The temperature at which suchcondensation takes place is called the Dew Point. Whencondensation takes place near the surface (and not onthe ground) the result is usually mist or fog. Whencondensation takes place at some distance from theground, clouds are formed. When water vapour iscondensed...