SUBJECT : GEOGRAPHY ROTATION AND REVOLUTION 2017-2018 This paper consists of 5 printed pages. 1. Name the motions of the earth. A. They are Rotation and Revolution. 2. What is Rotation? A. Rotation is the movement of the earth around its axis once in 24 hours causing day and night.(diurnal motion) ( 1 )
3. What are the effects of Rotation? A. The effects of rotation are : a) Parts of the Earth have day and parts of the earth have night-results in the occurrence of day and night b) It creates a centrifugal force which results in the shape of the earth, being an oblate spheroid (flattened at the poles and bulging at the equator c) It causes the deflective action of winds and ocean currents.winds get deflected to their right in the northern hemisphere and to their left in the Southern Hemisphere.(This is due to the Coriolis force) d)the moon sun and stars appear to move from East-West(the earth rotates from west to east) e) Tides occur twice daily and progress west ward. f)the Sun appears to rise in the East and set in the West. 4. Why does the speed of rotation decrease as we go towards the pole? A. The speed of rotation decreases as we go towards the pole because the earth is an oblate spheroid,the earth has a bulge in the centre and so there is more area to be covered in the same 24 hours whereas at the poles there is lesser area to be covered. 5. Mention the effects of the differences in the earth s speed of rotation. A. The differences in the earth s speed to rotation have important consequences :- a) It affects the general circulation of the atmosphere. The moving air in the northern hemisphere is deflected to the right and in the southern hemisphere it is deflected to the left. b) It also affects the movements of the ocean currents. c) I results in the bulge at the equator and the flattening at the poles. 6. What is meant by the earth s axis? A. The earth s axis is inclined at 66 ½ o from the plane of orbit. 7. What is the effect of the Earth,s axis? A The affect of the earth s axis is that the poles are presented alternately to the direct rays of the sun thereby resulting in seasons. 8. What is the Coriolis force? A. Coriolis force is created as a result of rotation due to which there is deflection of the prevailing winds and ocean currents. 9. What is the Centrifugal Force? A. It is a force which is generated as a result of rotation,. This causes the earth to be slightly flattened at the poles and slightly bulged at the equator. 10. What is Twilight? A. The faint light which illuminates the various parts of the earth before sunrise and sunset is called twilight. It occurs due to the reflection of the sun s light from the upper layers of the atmosphere. ( 2 )
REVOLUTION 11. What is Revolution? A. Revolution is the movement of the earth around the sun once in 365 ¼ days causing a change of seasons. 12. What are the effects of Revolution? A. The effects of revolution are :- 1. The change of seasons 2. The varying lengths of day and night. 3. The changing altitude of the midday sun at different times of the year. 13. How many days are there is a leap year? A. 366 days. 14. What do the following mean : - A. a) Solstice - sun standing still b) Tropic - means turning point c) Equinox - equal night ( 3 )
15a. On which day does the direct rays of the sun reach the Tropic of Cancer? A. On June 21 st. b. What is that position called? Why? A. That position is called the summer solstice because the direct rays of the sun fall on the Tropic of Cancer. The circle of illumination cuts the latitudes unequally. The greater part of the latitudes experience a longer duration of daylight hence it experiences summer. c. Name the areas that have continuous daylight on June 21st. A. The area that has continuous daylight on this day is all the places north of 66 ½ o N of Arctic circle. d. Which area will have six months of day of June 21 st. A. The north pole 90 o N will have six months of day. e. During the same time (21 st June) which area will have 6 months of night? Why? A. The south pole 90 o S will experience 6 months of night. The is because the Southern hemisphere is turned away from the sun and the sun s rays strike that part of the earth at small angles, hence continuous darkness. 16. When does the Tropic of Capricorn have (summer) or the direct rays of the sun? A. December 22 nd. 17. State two effects of West to East rotation of the earth. A. 1. Sun rises in the east and sets in the west. 2. If a stone is dropped it will fall slightly towards the East. 18. Briefly define the following terms and mention the dates on which they are experienced. A. 1. Solstice : means sun standing still. 2. It is experienced on June 21 st, summer solstice and December 22 nd. 3. On June 21 st, the sun s direct rays fall on the Tropic of Cancer, therefore the Northern hemisphere experiences summer with longer days. 4. On December 22 nd, the sun s rays are on the Tropic of Capricorn which then experiences summer. Perihelion is when the earth is closest to the sun in its orbit around the sun. This takes place on January 3 rd. The earth is 147 million km. away from the sun. Aphelion is when earth is farthest from the sun in its orbit around the sun. This takes place on July 4, the earth is 152 million km. sway from the sun. 19. Explain full the meaning of the term Equinox. A. 1. Equinox means equal night. 2. This phenomenon takes place on September 23 rd. Autumnal equinox and March ( 4 )
21 st, Vernal / Spring equinox. 3. On these days the sun s rays are directly on the equator. 4. The circle of illumination cuts all the latitudes into 2 equal parts thus all the latitudes from 0 o to 90 o N / S experience 12 hours day and 12 hours night or equal day and night. 20. The region beyond the Arctic circle is known as the Land of the Midnight Sun explain why? A. This is because for the m the sun does not rise or set on 21 st June. At the north pole there will be six months of daylight. The sun will be seen always above the horizon at a low angle. ( 5 )
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