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WBBSE 9th Class Social Science Solutions Geography & Environment Chapter 2 Movements of the Earth

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WBBSE 9th Class Social Science Solutions Geography & Environment Chapter 2 Movements of the Earth

West Bengal Board 9th Class Social Science Solutions Geography & Environment Chapter 2 Movements of the Earth

WBBSE 9th Class Geography & Environment Solutions

Salient points – At a Glance

  1. Every planet of the solar system rotates on its own axis and revolves around the Sun.
  2. Speed of rotation of Venus is less than the other planets of the solar system (equal to 243 Earth days).
  3. The main statement of the Geocentric Theory is that the Sun and the planets are moving around the Earth. Although, now this concept has been proved wrong.
  4. According to the Heliocentric Theory, the planets are moving around the Sun.
  5. The main proponents of Heliocentric Theory were Nicolaus Copernicus, Galileo and Kepler.
  6. In 1687, Sir Issac Newton proved by his law of gravity that the Earth has two motions-rotation and revolution, which are in action simultaneously.
  7. The average distance of the Earth from the Sun is 150 million km.
  8. In 1851, Leon Foucault, a French physicist, demonstrated an experiment at Pantheon Church in Paris, France to prove the rotation of the Earth.
  9. Speed of the Earth’s rotation is different on the different latitudes, 1675 km/hr at the Equator, 1533 km/ hr at the Tropic of Cancer and Capricorn, 666 km/hr at both the Arctic and Antarctic Circle and 0 km/ hr at the two Poles.
  10. In 1835, GD Coriolis, a French mathematician first proved that the rotation of the Earth is responsible for the generation of a centrifugal force which is known as Coriolis force.
  11. Under the influence of centrifugal force due to the rotation of the Earth, the ocean currents and planetary winds deflect from their direction in both the hemispheres, which is known as Ferrel’s law.
  12. Circumference of the Earth’s orbit 960 million km.
  13. The axis of the Earth is an imaginary line that joins the North and the South Pole and passes through the centre of the Earth.
  14. The phenomenon of equal length of day and night all over the Earth, is called equinox. The days and nights are of equal duration everywhere on Earth on 21 March and 23 September. These days are called vernal equinox in the northern hemisphere and autumnal equinox in the southern hemisphere respectively.
  15. On 21 June, sunrays fall vertically over lled the Tropic of Cancer, and the day is summer solstice.
  16. On 22 December, sunrays fall vertically over the Tropic of Capricorn, and the day is called winter solstice.
  17. The average velocity of the Earth’s revolution is 30km/sec.
  18. Aurora in the north polar region and the south polar region are known as Aurora Borealis and Aurora Australis respectively.
  19. The Earth is farthest from the Sun (approximately 152 million km) on July 4. This phenomena is called Aphelion.
  20. The Earth (approximately January 3. This Perihelion. is closest to the Sun 147 million km) on phenomena is called

TOPIC – A

Rotation of the Earth

Long Answer Type Questions

1. How can we prove that the Earth has rove that the Earth diurnal motion?
Ans. Evidences of Earth’s diurnal motion: The movement of the Earth on its axis from west to east in an anti-clockwise direction within a duration of 24 hours is known as rotation of the Earth or Earth’s diurnal motion. The fact that the Earth has diurnal motion can be proved by the following points-
  1. Earth is shaped like an oblate sphere: When a circular object rotates constantly on its axis, its centre bulges outwards, while the top and the bottom ends get flattened. The same happens on the Earth. The Earth bulges at the Equator and is flattened at the Poles.
  2. Occurrence of day and night in a cyclic pattern: Due to the fact that the Earth rotates on its axis within a span of 24 hours, all places on Earth experience days and nights in a cyclic pattern. If the Earth had not been rotating, the side facing the Sun would have had eternal daylight while the opposite side would have experienced eternal night.
  3. Observing a stone falling from a certain height: When a stone is dropped from a certain height, it does not fall vertically in a straight line. Instead it shifts somewhat to the east. This proves that the Earth rotates from the west to the east.
    In the given figure, a stone is dropped from point A. It should have touched the Earth’s surface at point A’. But due to Earth’s rotation it gets deflected towards the East and touches the Earth’s surface at point B instead.
  4. Pictures taken from artificial satellites: Several man-made satellites sent to outer space have captured pictures of the Earth, which are a proof of the fact that the Earth is rotating on its axis.
  5. Rotation of the other planets on their axes: The other planets of the solar system like Venus, Mars, Jupiter etc. rotate on their respective axes. Since the Earth is also a planet of the same solar system, it is therefore deduced that the Earth too rotates on its axis.
  6. Change in direction of wind and sea waves: The direction of sea waves and wind is not straight in either hemisphere while moving from the high pressure belts to low pressure belts. Instead the direction shifts to the left in the southern hemisphere and to the right in the northern hemisphere. This change in direction occurs due to the rotation of the Earth.
  7. Regular occurrence of tides: Tides occur on Earth due to the gravitational pull of the Moon. If the Earth would not have been rotating, any place on Earth would have experienced near tidal bulge once in every 27 days. It is only because of Earth’s rotation that near tidal bulge occurs on a daily basis.
  8. Foucault’s experiment: French scientist Foucault (1851) demonstrated an experiment with a pendulum and proved that the Earth is rotating.
2. What are the results of the diurnal motion of the Earth?
Ans. Results of the diurnal motion of the Earth: The rotation of the Earth on its axis in 23 hours 56 minutes 4 seconds is called the diurnal motion of the Earth or rotation of the Earth. This is an anti-clockwise movement. The results of this diurnal motion are as follows-
  1. Cyclic occurrence of days and nights: The Earth is round in shape and has no light of its own. The rays of the Sun are the only source of heat and light for the Earth. Therefore, during the rotation of the Earth, one half of the Earth receives the rays of the Sun and it is daytime in that area, while the region which remains in darkness has night.
  2. Sunrise and sunset: Due to the fact that the Earth rotates from west to east, the Sun rises in the east and sets in the west.
  3. Calculation of time: One complete rotation of the Earth takes almost 24 hours or 1 complete day. Each hour is divided into 60 minutes and each minute into 60 seconds for easier calculation of time.
  4. Change in direction of sea waves and wind movement: The centrifugal force generated due to the rotation of the Earth is called the Coriolis Force. This Coriolis Force causes deflection in the direction of sea waves and winds in both the hemispheres.
  5. Formation of tides: As a result of the gravity, both the Sun and the Moon exert gravitational force over the Earth. However, since the Moon is closer to the Earth than the Sun, it exerts greater gravitational force on the Earth than the Sun. Due to the rotation of the Earth, the side facing the Moon experiences zenith tide, while the side opposite to that side of the Earth that faces the Moon experiences nadir tide. The other sides (apart from the one facing the Moon and opposite to the Moon) experience low tide.
  6. Existence of flora and fauna: If the Earth would not have been rotating, one part of the Earth would have always been away from the Sun. This side would not have received any light or heat. Therefore, nothing would have grown on this side of the Earth. On the other hand the side permanently facing the Sun would have got an abundance of heat and light, again making it impossible for life to sustain there. The rotation of the Earth is responsible for cyclic occurrence of day and night and equal distribution of heat and light, thus making the Earth a planet fit for habitation.
3. How do days and nights occur? Discuss the different phases of day and night on Earth.
Ans. Occurrence of days and nights: The Earth rotates from west to east on its axis. During rotation, the half of the Earth that faces the Sun experiences day and the half that remains away form the Sun experiences night.
Different phases of day and night: The different phases of day and night are-1. Morning and evening, 2. Dawn and dusk, 3. Midday and midnight.
  1. Morning and evening: Due to the rotation of the Earth, when a particular region crosses the circle of illumination of the Earth and faces the Sun, it experiences morning; and the region opposite to this point, which is away from the Sun, experiences evening.
  2. Dawn and dusk: Just before sunrise, the dust particles in the atmosphere reflect the Sun’s rays and a diffused light spreads over the eastern sky. This time of the day is known as dawn. Again, just after sunset, the dust particles in the atmosphere reflect the Sun’s rays. As a result, a diffused light spreads over the western sky. This time of the day is known as dusk.
  3. Midday and midnight: When the Sun is overhead a place, this place is said to be having a midday; and the place that lies on the opposite side of this point is said to be having a midnight.
4. Why do winds and ocean currents get deflected?
Ans. Causes of deflection of winds and ocean currents: Planetary winds and ocean currents get deflected due to the Earth’s rotation. According to William Ferrel’s (American scientist) law, moving objects on the Earth’s surface, such as winds and ocean currents, get deflected to the right in the northern hemisphere and to the left in the southern hemisphere. A detailed explanation of this phenomenon is given below.
The circumference of the Earth decreases gradually from the Equator to the Poles.The speed of the Earth’s rotation is also the maximum at the Equator, and decreases gradually towards the Poles.Therefore, when winds blow towards the Equator, from any region in the northern hemisphere their speed is less in comparison to that of the winds blowing in the equatorial region. However, as they try to maintain their original speed, they deviate from their path of flow and deflect to the right. Similarly, winds blowing from the Equator towards the north also get deflected to their right. Likewise, winds blowing from the Equator towards the south get deflected to their left. For example, trade winds blowing towards the equatorial doldrums in the northern hemisphere deflect to the right are known as north-east trade winds and deflect to the left in the southern hemisphere are known as south-east trade winds.
Ocean currents too get deflected in the northern and southern hemispheres in the same manner due to the same reason.
5. How did scientist Leon Foucault prove that the Earth rotates? What is a leap year?
Ans. Foucault’s experiment: In 1851, French scientist Foucault demonstrated an experiment by fixing a pin underneath a pendulum bob, and suspending it from Pantheon church in Paris with a 67 m long wire, over some sand. He noticed that though the pendulum was oscillating from north to south in a fixed path, the markings on the sand were gradually moving from west to east. This proved that the Earth rotates from west to east, otherwise the pendulum would have been on the same marked spot each time.
If you take a look at the figure, you will notice that the pin will move from A to A’ first, then from B to B’, then C to C’, then D to D’, then E to E’, and exactly after 24 hours, it will return to AA’. If all the points are joined, you will find that they form an arc. This phenomenon occurs due to the rotation of the Earth.
Leap year: The time taken by the Earth to complete one revolution around the Sun is 365 days 5 hours 48 minutes and 46 seconds. This is known as one solar year. However, for easier calculation, the time taken for one revolution is taken to be 365 days. The remaining 6 hours (5 hours 48 minutes and 46 seconds) is taken together to form one day every 4 years (6 × 4 = 24 hours), and is added to the month of February. Therefore, after every four years, February has 29 days and the year has 366 days. This is known as a leap year. For example, the years 2000, 2004, 2008, 2012, 2016, etc. are leap years. If the digits constituting the year can be divided by 4, it is a leap year.
6. Write about the movements of different planets in the solar system.
Ans. Movements of different planets in the solar system: Each planet of the solar system has two motions or movements. One of them is rotational movement, where the planets rotate around their own axis. In another motion the planets revolve around the Sun along their orbit. This heliocentric motion is called revolution.
Rotation of Mercury, Earth, Mars, Jupiter, Saturn, Neptune is anti-clockwise and the rotation of Venus and Uranus is clockwise.
The period of rotation of the planets in the solar system are different and even their revolutions are unique. Generally seen, the period of a planet’s rotation is less than its revolution. But, Venus is exceptional. Rotational period of Venus is equal to 243 Earth days but revolutional period of this planet is equal to 225 Earth days, that means its days are longer than its year.
Rotational and revolutional periods of the planets are given in the table-
Planet Period of rotation (according to Earth’s time) Period of revolution (according to Earth’s time)
1. Mercury 58 days 15 hours 88 days
2. Venus 243 days 225 days
3. Earth 23 hours 56 minutes 365 days
4. Mars 24hours 37 minutes 687 days
5. Jupiter 9 hours 50 minutes 12 years
6. Saturn 10 hours 14 minutes 29 years 7 months (approx)
7. Uranus 17 hours 14 minutes 84 years
8. Neptune 16 hours 7 minutes 165 years
7. Write an observational history about the motions of the Earth from ancient time to present.
Ans. Observational history about the motions of the Earth: From the ancient time, scientists and scholars had different opinions about the motions of the Earth. Philosophers, scientists, geographers, mathematicians, astronomers of the ancient time explained various ideas about the motion of the Earth based on various facts. But, there are so many differences among the ideas. Geocentric and heliocentric concepts had been developed on the basis of these differences.
  1. Geocentric theory: In ancient time, scholars believed the idea of the geocentric universe. They believed that the Sun, Moon and the stars moved around the Earth along their circular orbits. Main proponents of the idea were Thales, Anaximander, Plato, Ptolemy and others. Plato thought that the Earth was the centre of universe and all the heavenly bodies or stars moved around the Earth. But at present, this idea has been dissaproved.
  2. Heliocentric theory: The great Indian astronomer Aryabhatta first declared that the Earth is not stationary, it is dynamic and the Earth rotates everyday around its axis. Later, Nicolaus Copernicus, Kepler and Galileo established this doctrine. Nicolaus Copernicus, a Polish astronomer first stated this fact in his book ‘De revolutionibus orbium coelestium’. He said that the Earth I was not at the centre of the universe. All planets move around the Sun. Later, Kepler proposed the orbits of the planets are eliptical. Galileo Galilei agreed with the heliocentric theory observing the movement of satellites through a telescope. Later, in 1687 Sir Issac Newton proved by his law of gravitation that the Sun is larger than the Earth and other planets, so the Earth and the other planets are moving around the Sun due to the gravitational attraction of the Sun. Edmond Halley also agreed the Earth moves around the Sun, after observing the movement of the comet.

Short Explanatory Answer Type Questions.

1. What do you mean by Coriolis force or Coriolis effect?
Ans. Due to the rotation of the Earth, winds and ocean currents on the surface of the Earth do not flow in a straight line, but get slightly deflected from their direction of movement. The force due to which winds or ocean currents get deflected is known as Coriolis force or Coriolis effect. This phenomenon has been named after the French mathematician Gaspard-Gustave de Coriolis, who discovered it in 1835.
2. Why do winds and ocean currents deflect due to the the Coriolis force?
Ans. The effect of the Coriolis force is less in the polar regions as compared to that in the equatorial region. The speed of Earth’s rotation is also more in the equatorial region and less at the polar regions. Due to this difference in the rotational speed, winds in the equatorial region are faster than winds in the polar regions. At the Equator, the winds blowing from both sides try to retain their original speed and thus get deflected. Due to this, winds blowing from the Equator towards the Poles get deflected to the right in the northern hemisphere and to the left in the southern hemisphere. Ocean currents are also get deflected in the same way.
3. What do you mean by the apparent daily motion of the Sun?
Ans. Since its origin, the Earth rotates on its axis while revolving around the Sun. We live on the Earth and it seems to us that the Earth is fixed, and the Sun is moving east to west around it. In reality, as the Earth rotates from west to east, the Sun seems to move from east to west. This apparent movement of the Sun around the Earth is called the apparent daily motion of the Sun.
4. Discuss the importance of the inclination of the Earth’s axis.
Ans. The Earth’s axis is inclined at an angle of 66½° with respect to the Earth’s orbital plane. Due to this the following happen- (1) Duration of days and nights change, (2) difference in temperature causes change in seasons, (3) the angle at which the Sun’s rays fall on the Earth are different at different places, (4) the northern and southern hemispheres have opposite seasonal pattern, (5) the Sun appears bigger or smaller at different times of the year.
5. What is the speed of the Earth’s rotation on the different important lines of latitude?
Ans. Speed of Earth’s rotation on different important lines of latitude are as follows-
Latitude Speed of rotation
0° 1,670 km/hr
23½°N and S 1,531 km/hr
66½°N and S 666 km/hr
90°N and S 0
6. What is Ferrel’s law?
Ans. The speed of the Earth’s rotation decreases as we move from the the Equator towards the Poles. This gives rise to Coriolis force, which causes all objects on the Earth’s surface (wind, ocean currents, etc.) moving from the northern hemisphere to southern hemisphere and vice versa to deflect from their original path of motion. Winds and Ocean Currents deflect to the right in the northern hemisphere and to the left in the southern hemisphere,
American scientist William Ferrel established this law in 1855, thus it is known as Ferrel’s law.
7. Why is the Earth’s rotational speed different in different places?
Ans. The Earth completes one rotation around its axis in 23 hours 56 minutes and 4 seconds. As the circumference of the Earth is different at different lines of latitude, the rotational speed of the Earth is different at different places. As the Earth’s circumference is the greatest at the equatorial region, the rotational speed is also highest at the Equator (about 1670 km/hr). From the Equator to the Poles, the circumference of the Earth gradually decreases, and thus, the rotational speed of the Earth decreases from the Equator to the Poles.
8. ‘The shape of the Earth is like an oblate spheroid.’- How does this testify the existence of the Earth’s rotation?
Ans. The rotation of the Earth on its axis gives rise to centrifugal force. Due to this force, liquid and gaseous matter from the polar regions moved to the equatorial region, causing this region to bulge out. On the other hand, the rise of centripetal force in the polar regions have caused them to flatten. Therefore, it can be concluded that the Earth’s rotation is responsible for its oblate spheroid shape. As the rotational speed of planets like Jupiter and Saturn is much more than that of the Earth, the Poles of these planets are much more flattened compared to the Earth.
9. Why cannot we feel the Earth’s rotation?
Ans. We cannot feel the rotation of the Earth because of the following reasons-
  1. Equal rotational speed: We are moving at a speed equal to the speed of the rotation of the Earth. Thus it is not possible for us to feel the Earth’s rotation.
  2. Gravitational force: The gravitational force of the Earth pulls all the objects on the Earth’s surface towards its centre. Due to this force, we do not fly off the surface of the Earth in spite of its rotation.
  3. Size of the Earth: The Earth is a huge sphere and we are so small compared to the size of the Earth. So, it is not possible for us to sense the Earth’s rotation.
10. Temperature decreases from the Equator towards the Poles.’ Explain.
Ans. The rays of the Sun do not fall equally on all parts of the Earth due to various reasons, like, the shape of the Earth, its rotation, etc.
The sunrays fall vertically on the equatorial region, spreading over a smaller area and are slanted at the Poles, spreading er a larg area. Besides, as the rays have to travel over a longer distance in order to reach the polar regions, they lose much of their heat in the process. Hence, temperature gradually decrease as we move from the Equator to the Poles.
11. What would have happened if there was no rotation of the Earth?
Ans. If there was no rotation of the Earth- (1) There would have been no sunrise and sunset and thus formation of day and night would not have occurred. (2) The time could not have been determined. (3) The tides would not have formed twice a day. (4) The shape of the Earth would not have been oblate spheroid. (5) Without the Earth’s rotation, Sun facing side of the Earth would, always remain enlightened and other half would always have darkness and coldness prevailing. (6) Life would not have been possible due to extreme inconsistencies of the temperature in different parts on the Earth.

Short Answer Type Questions

1. What is the rotation of the Earth?
Ans. The Earth rotates on its axis, from west to east within a span of about 24 hours. This motion is known as the rotation of the Earth.
2. What is solar day?
Ans. The time difference between two middays (12pm) on a single longitude is known as solar day. The span of one solar day on Earth is 24 hours.
3. What is a sidereal day?
Ans. The time taken by Earth to complete one rotation on its own axis, so that a distant star (except the Sun) appears at the same position on a single longitude twice is known as sidereal day. One sidereal day is approximately 4 minutes shorter than a solar day.
4. What is Ferrel’s law?
Ans. In 1855, American scientist William Ferrel stated that ocean currents and wind gets deflected to the right in the northern hemisphere and to the left in the southern hemisphere due to the rotation of the Earth. This is that known as Ferrel’s law.
5. What is Coriolis force?
Ans. In 1835, French mathematician, GaspardGustave de Coriolis, proved that the rotation of the Earth is responsible for the creation of a Centrifugal force. This force was later named as Coriolis force.
6. Where is the rotational speed of the Earth fastest and where is it slowest?
Ans. The speed of rotation of the Earth is fastest in the equatorial region, whereas, it is the slowest at the Poles.
7. What is dawn?
Ans. Just before sunrise, the darkened part of the Earth crosses the circle of illumination and receives the first light of day. This is known as dawn.
8. What is dusk?
Ans. After sunset, the lightened part of the Earth enters the darkened area, after crossing the circle of illumination. This is known as dusk.
9. What are the effects of the Earth’s rotation?
Ans. The effects of the Earth’s rotation are- (1) the occurrence of days and nights, (2) change in direction of ocean currents and wind, (3) creation of tides, (4) the occurrence of sunrise and sunset in a cyclic order, etc.
10. What is shadow circle?
Ans. Since the Earth is round, one half the Earth receives sunlight and remains illuminated, while the other side does not get sunlight and remains dark. The imaginary line of longitude which is the dividing line between the illuminated and the darkened portions of the Earth is known as shadow circle or circle of illumination.
11. Even though the Earth is rotating, why are not we falling down?
Ans. The Earth is constantly rotating from west to east. However, the gravitational pull of the Earth attracts every object towards its centre. Hence we do not fall down even though the Earth is rotating continuously.
12. Which planets rotate in a clockwise direction?
Ans. Venus and Uranus rotate in a clockwise direction.
13. Which planet’s period of rotation is more than the period of revolution?
Ans. The rotational period of Venus is more than the period of revolution, where the rotation and revolution periods are equal to 243 and 225 Earth days respectively.
14. On which part of the Earth the effects of Coriolis force is the highest and where is it the lowest?
Ans. The effects of the Coriolis force is highest at the Poles and lowest at the Equator.
15. What do you mean by apparent motion?
Ans. If a still object appears in motion, it is called the object’s apparent motion.
16. ‘Life would not have been possible on the Earth without rotation.’ State two reasons in support of this statement.
Ans. ‘Life would not have been possible on the Earth without rotation. Two reasons in support of the statement are- (1) Without Earth’s rotation, one side of the Earth would have been burnt by the Sun’s heat and the other side would have been frozen, destroying any forms of life. (2) Without rotation, a balance in temperature would not have been possible, making survival of lifeforms impossible.
Therefore, one of the main reasons for the survival of life on Earth is its rotation.

Multiple Choice Type Questions [MCQ type]

Write the correct answer from the given alternatives

1. The rotational speed of the Earth at the Equator is-
A. 1600 km
B. 1630 km
C. 1650 km
D. 1670 km
Ans. D
2. The angle of inclination of the Earth’s axis towards the orbital plane is-
A. 23½°
B. 30°
C. 60°
D. 66½°
Ans. D
3. The Earth’s rotation causes-
A. formation of tides
B. change of seasons
C. change of years
D. formation of days and nights
Ans. A
4. The longest day at the Equator is of-
A. 11 hours
B. 12 hours
C. 13 hours
D. 12½ hours
Ans. B
5. Mercury completes one revolution around the Sun in-
A. 90 days
B. 100 days
C. 88 days
D. 85 days
Ans. C
6. At the Poles, the speed of rotation of the Earth is-
A. 660 km/h
B. 1536 km/h
C. 1674 km/h
D. 0 km/h
Ans. D
7. In relation to the Sun, the Earth is-
A. 1.3 million times smaller
B. 1.2 million times smaller
C. almost half in size
D. almost same in size
Ans. A
8. The speed of rotation of the Earth in Kolkata is-
A. 1536 km/h
B. 1674 km/h
C. 0 km/h
D. 666 km/h
Ans. A
9. The total number of motions of the Earth is-
A. one
B. two
C. three
D. four
Ans. B
10. Mercury completes one rotation on its axis in-
A. 55 hours
B. 58 hours
C. 58 days 15 hours
D. 59 days
Ans. C
11. Period of Neptune’s revolution is-
A. 165 years
B. 3160 years
C. 155 years
D. 150 years
Ans. A
12. Rotation of the Earth causes-
A. formation of days and nights
B. variation in the length of days and nights
C. change of year
D. change of seasons
Ans. A
13. The speed of rotation of the Earth is highest at-
A. 45° latitude
B. the Equator
C. polar region
D. sub-polar region
Ans. B
14. Length of the solar day than the sidereal day is-
A. 3 minutes 52 second less
B. 33 minutes 54 seconds more
C. 3 minutes 56 seconds more
D. 3 minutes 58 seconds more
Ans. C
15. If the Earth’s rotation stops suddenly, all objects will be scattered-
A. eastwards
B. westwards
C. northwards
D. southwards
Ans. A

Very Short Answer Type Questions

Fill in the blanks with suitable words

1. In comparison to the equatorial region, the speed of rotation of the Earth at the Pole is………
Ans. lesser
2. According to ………. law, wind gets deflected towards the right in the northern hemisphere.
Ans. Ferrel’s
3. The ……… region experience 6 months of continuous night.
Ans. polar
4. The speed of rotation at the Poles is ……….
Ans. almost 0
5. The Sun rises in the east because in reality, the Earth rotates from ……… to ……….
Ans. west; east
6. ……… is one complete rotation of the Earth on its own axis in 24 hours.
Ans. Solar day
7. The Indian scientist who first put forward a Sun-centric model of the universe was ………..
Ans. Aryabhatta
8. ………. was the first person to prove that the Sun is fixed and the planets are revolving around it.
Ans. Copernicus
9. ………. proved that both motions of the Earth occur simultaneously.
Ans. Sir Isaac Newton
10. The boundary between the lit half and the dark half of the Earth is marked by the……..
Ans. circle of Illumination
11. Another name of the Earth’s rotation is …….
Ans. diurnal motion
12. The opposite or antipode side of the place of zenith tide experiences ………. tide.
Ans. nadir

If the statement is true, write T and if false, write ‘F against the following

1. The Earth has only one motion.
Ans. F
2. Days and nights occur due to the annual movement of the Earth.
Ans. F
3. The rotation of the Earth is the fastest at the Equator.
Ans. T
4. Tides occur due to the revolution of the Earth.
Ans. F
5. Winds get deflected due to the Coriolis force.
Ans. T
6. The circular boundary line between light and darkness is known as latitude.
Ans. F
7. The Earth resembles an oblate sphere, due to its rotation.
Ans. T
8. The centrifugal force is created due to the rotation of the Earth.
Ans. T
9. The equatorial region of the Earth bulges out while the polar regions are flattened.
Ans. T
10. The South Pole faces the North Star.
Ans. F
11. Coriolis force is created due to the rotation of the Earth.
Ans. T
12. Ptolemy agreed with the Geocentric Theory.
Ans. T
13. The Sun rises in the east and sets in the west due to the Earth’s revolution.
Ans. F
14. The speed of rotation of the Earth at Kolkata is greater than that at London.
Ans. T
15. The speed of Earth’s rotation at the Equator is 6147 km/hour.
Ans. F

Answer in one or two words

1. Which movement of the Earth is responsible for causing days and nights?
Ans. Rotational movement.
2. In which part of the Earth is the speed of rotation minimum?
Ans. The polar region.
3. Who proved that ‘the Earth rotates round the Sun?’
Ans. Galileo.
4. What is the boundary line where the illuminated and the darkened portions of the Earth meet?
Ans. The circle of illumination or shadow circle.
5. What is the direction of the Earth’s rotation?
Ans. West to east.
6. Who discovered the existence of gravitation force?
Ans. Sir Isaac Newton.
7. In which year did Sir Isaac Newton prove the movement of the Earth?
Ans. 1687.
8. What is the time taken by Jupiter to complete one rotation and one revolution?
Ans. 9 hours 50 minutes, 12 years.
9. What shape has the Earth assumed due to rotation?
Ans. Geoid shape.
10. What would have been the span of time between tides if the Earth would not have been rotating?
Ans. An interval of 27% days.

TOPIC – B

Revolution of the Earth

Long Answer Type Questions

1. What proof do we have about the revolution of the Earth?
Ans. Proof of the revolution of the Earth: The movement of the Earth on an elliptical orbit around the Sun, is known as the revolution of the Earth. The proofs of the revolution of the Earth are-
  1. Change in position of star: If we notice a group of stars in the night sky everyday, we will observe that the stars gradually move towards the west. After a few days, the older stars disappear from the sky and a new set of stars appear. The older set of stars appear again in the sky after a year. This proves that the Earth revolves around the Sun and after a year gradually comes back to the position it started from.
  2. Change in the position of sunrise and sunset: Due to the Earth’s revolution, an apparent annual movement of the Sun is noticed. The Sun rises exactly in the east and sets in the west from 21 March and 23 September. On the other days of the year, the Sun rises and sets with a slightly northward or southward shift. If the Earth had not been revolving, the Sun would have been rising and setting exactly in the east and the west for the entire year.
  3. Change of seasons and the duration of days and nights: Due to the revolution of the Earth, there is change of seasons on Earth. The duration of days and nights also varies throughout the year due to the same reason.
  4. Observing the revolution of the other planets: With the help of powerful telescopes scientists have observed that the other planets like Venus, Mars, Jupiter, etc. are revolving around the Sun. As the Earth is a planet of the same solar system like the rest, therefore it can be concluded that the Earth is also revolving around the Sun.
  5. Pictures taken from satellites: The pictures taken from satellites prove that the Earth is revolving around the Sun.
2. What are the results of the Earth’s annual movement or revolution?
Ans. Results of the revolution of the Earth: Revolution of the Earth is the movement of the Earth around the Sun, while rotating on its axis from west to east in an anti-clockwise pattern within a span of 365 days and 6 hours. The results of the revolution of the Earth are-
  1. Change in the duration of days and nights: The Earth is inclined on its axis at an angle of 66½°. As a result of this inclination, the rays of the Sun are sometimes vertical on the Tropic of Capricorn in the southern hemisphere and sometimes on the Tropic of Cancer in the northern hemisphere. This causes change in the duration of days and nights in both hemispheres.
  2. Change of seasons: The distance of the Earth from the Sun changes during the revolution. Since the Earth is inclined at an angle of 66½° and is somewhat circular in shape; the rays of the Sun do not fall in the same manner on all the parts of the Earth. Some parts receive direct rays of the Sun, while the rest may receive inclined rays of the Sun. This is responsible for the variation of heat received by the places, that causes difference of seasons. Generally, the hemisphere receiving the direct sunrays experiences summer, while the other receiving the inclined sunrays experiences winter.
  3. Apparent annual movement of the Sun: The Sun rises exactly in the east and sets exactly in the west on 21 March and 23 September. On the other days the Sun rises and sets shifted slightly to the north or the south. This northward or southward movement of the Sun is known as the apparent annual movement of the Sun.
  4. Change in position of stars: If noticed closely, stars in the night sky shift their position gradually from east to west. After a few days, the stars disappear from the sky and a new set of stars appear. After a year, the same stars are again seen in the sky, in the same position.
  5. Year and leap year: The time of one complete revolution of the Earth is 365 days 5 hours. 48 minutes 46 seconds, which is called a year. But we consider 365 days to make the calendar year for easier calculation. So, each year there is an excess of roughly 6 hours. Therefore, every fourth year is added by (6 × 4) 24 hours, i.e. 1 day in the month of February which consists of 29 days. Thus, this year with 29 days in February is called a leap year consisting of 366 days.
  6. Creation of temperature zone: The variation in incidence of sunrays due to the revolution of the Earth, causes variation in temperature in the different places of the Earth throughout the year. Based on this variation in the temperature the Earth is divided into three heat zones- torrid zone, temperate zone and frigid zone.
3. What are the reasons for season change on the Earth?
Ans. Reasons for season change on the Earth: The various regions of the Earth do not receive equal amount of sunlight throughout the year. Thus when one place experiences summer another might experience winter. A year is divided into seasons on the basis of this variation. The reasons that lead to seasonal changes are-
  1. Revolution of the Earth: The Earth rotates upon its own axis in particular path and in a particular direction (anti-clockwise). The Earth also revolves around the Sun in a particular path, taking a particular amount of time. Variations in the amount of sunlight received amongst the various regions of the Earth is due to this reason. As a result, seasons change.
  2. Inclination of the Earth at 66½° angle on its axis: The Earth is inclined at an angle of 66% on its axis with respect to its orbital plane. This is one of the causes behind the change in duration of days and nights. This creates a difference temperature that leads to seasonal change. For example, if the days are longer and nights shorter, then the total heat absorbed by the Earth during the day cannot be radiated out. Therefore, the temperature of that area increases.
  3. Geoid shape of the Earth: The Earth is not a perfect sphere, it is geoid in shape. This is the reason for the rays of the Sun falling directly on some areas and tangentially on others. The direct rays of the Sun heat up the Earth faster than the tangent rays, that creates a variation in temperature and season.
4. Give an idea about Perihelion and Aphelion.
Ans. Perihelion: The Earth is closest to the Sun on 3 January. The distance between the Earth and the Sun is approximately 147 million km.
This position of the Earth from the Sun, on its orbit is called Perihelion.
Result: (1) The distance between the Sun and the Earth reduces during this position. (2) The Sun appears larger in the northern hemisphere during this time. (3) The rotation speed of the Earth increases during this position.
Aphelion: The distance between the Earth and the Sun is maximum on 4 July. The distance is approximately 152 million km. This position of the Earth from the Sun is called Aphelion.
Result: (1) The distance between the Sun and the Earth increases during this position. (2) Due to Aphelion, the Sun appears smaller in the southern hemisphere, during summers. (3) The rotational speed of the Earth decreases slightly during Aphelion.
5. Why does the duration of days and nights change?
Ans. Reasons behind the change of duration of days and nights: 21 March and 23 September are the two days apart from which the duration of days and nights on the Earth vary. This is because of- (1) the revolution of the Earth, (2) the position of the Earth on its axis along its orbital plane, (3) the geiod shape of the Earth, (4) elliptical shape of the Earth’s orbit, (5) the position of the Earth’s Poles towards the North Star, (6) the sun’s apparent daily and annual movement etc.
The Earth stands in different positions in its orbit on different periods of the year. The several reasons for the change in duration of days and nights are given below-
  1. During summer solstice: On 21 June the position of the Earth is such that the northern hemisphere is inclined towards the Sun and the Tropic of Cancer receives direct sunrays. Hence, on this day the northern hemisphere experiences the longest day and the shortest night. The southern hemisphere on the other hand experiences the complete opposite phenomena.
  2. After summer solstice: After 21 June, the position of the Earth gradually changes and the southern hemisphere gradually starts shifting towards the Sun. The sunrays fall directly on the southern hemisphere and thus the days become longer and the nights. shorter, while completely the opposite happens in the northern hemisphere.
  3. During autumnal equinox: On 23 September, the position of the Earth on its orbit is such that both the hemispheres are equidistant from the Sun. Hence days and nights are of equal duration in both hemispheres. It is called autumnal equinox because it marks the end of the rainy season and begining of autumn.
  4. After autumnal equinox: After the autumnal equinox (September 23), the southern hemisphere comes even closer to the Sun while the northern hemisphere shifts further away from it. The duration of days become longer and nights shorter in the southern hemisphere and it is just the opposite in the northern hemisphere.
  5. During winter solstice: On 22 December, the sunrays fall directly on the Tropic of Capricorn. This is the longest day of the southern hemisphere and just the opposite happens in the northern hemisphere.
  6. After winter solstice: After 22 December, the southern hemisphere shifts away from the Sun, while the northern hemisphere moves towards the Sun. This causes the shorter days and longer nights in the southern hemisphere.
  7. During vernal equinox: On 21 March the position of the Earth on its orbit is such that the both northern and southern hemispheres are equidistant from the Sun. Thus, duration of days and nights are equal.
  8. After vernal equinox: The northern hemisphere gradually shifts towards the Sun, while the southern hemisphere shifts away from the Sun. This makes nights shorter and days longer in the northern hemisphere and just the opposite in the southern hemisphere.
6. What do you mean b by seasonal cycle? Explain the seasonal cycle briefly.
Ans. Seasonal cycle: The apparent northward and southward movement of the Sun and the variation in the length of days and nights are caused by the revolution of the Earth. This creates a difference in temperature in different places over the Earth which, in turn, affects the weather and climate of that region. On the basis of this variation of temperature, a year has been divided into four seasons-summer, autumn, winter and spring. The cyclic change of these seasons is known as seasonal cycle.
Explanation of seasonal cycle: Seasonal cycle or the cyclical change of seasons is explained below-
  1. Summer in northern hemisphere and winter in southern hemisphere: During one and a half months preceding and following 21 June, the northern hemisphere remains tilted towards the Sun, while the southern hemisphere remains away from the Sun. The northern hemisphere receives almost vertical rays of the Sun, while the southern hemisphere receives slanting rays. Hence the northern hemisphere experiences summer and the southern hemisphere experiences winter.
  2. Autumn in northern hemisphere and spring in southern hemisphere: After July, as the Earth moves around its orbit, the amount of sun’s rays received by the northern hemisphere decreases while the amount received increases in the southern hemisphere. Due to this, during one and a half months preceding and following 23 September, the northern hemisphere experiences autumn, and the southern hemisphere experiences spring.
  3. Summer in southern hemisphere and winter in northern hemisphere: During one and a half months preceding and following 22 December, the southern hemisphere remains tilted towards the Sun, while the northern hemisphere remains away from the Sun. The southern hemisphere receives almost vertical rays of the Sun, while the northern hemisphere receives slanting rays. Hence, from November to January, the southern hemisphere experiences summer and the northern hemisphere experiences winter.
  4. Spring in northern hemisphere and autumn in northern hemisphere: After January, as the Earth moves around its orbit, the amount of Sun’s rays received by the southern hemisphere decreases while the amount received increases in the northern hemisphere. Due to this, during one and a half months preceding and following 21 March, the northern hemisphere experiences spring and the southern hemisphere experiences autumn.
Two regions on the Earth’s surface do not experience change in seasons, they are- (1) The equatorial region receives vertical rays of the Sun throughout the year, thus it always experiences summer. (2) The North and South Poles receive slanting rays of the Sun throughout the year, thus these regions always experience winter.

Short Explanatory Answer Type Questions

1. Discuss the features of the Earth’s orbit.
Ans. The fixed path in which the Earth moves around the Sun is known as the Earth’s orbit.
The features of the Earth’s orbit are- (1) It is elliptical in shape. (2) Its circumference is about 960 million kilometre. (3) The centres of the Earth and the Sun lie on the same orbital plane. (4) The Sun is located in one of the loci of the Earth’s orbit.
2. Why does February have 29 days and the year has 366 days after every four years?
Ans. The time taken by the Earth to complete one revolution around the Sun is 365 days 5 hours 48 minutes and 46 seconds. This is known as one solar year. However, for easier calculation, the time taken for one revolution is taken to be 365 days. The remaining 6 hours (5 hours 48 minutes and 46 seconds) is taken together to form one day every 4 years (6 × 4 = 24 hours) and is added to the month of February. Therefore, after every four years, February has 29 days and the year has 366 days.
3. Why is the duration of winter less in the northern hemisphere?
Ans. On 3 January, the distance between the Earth and the Sun is minimum (about 147 million km). This is known as Perihelion. During this phase, the speed of the Earth’s revolution increases slightly and thus the Earth moves faster along its orbit. At this time, the northern hemisphere experiences winter season, while the southern hemisphere experiences summer. Thus, the duration of winter is less in the northern hemisphere.
4. Write differences between vernal equinox and autumnal equinox.
Ans. The differences between vernal equinox and autumnal equinox are as follows-
Point of difference Vernal equinox Autumnal equinox
1. Concept Divides all latitudes equally, and duration of day and night is equal everywhere. This is known as the vernal equinox in northern hemisphere. Divides all latitudes equally, and duration of day and night is equal everywhere. This is known as the autumnal equinox in the southern hemisphere.
2. Date It occurs on 21 March. It occurs on 23 September.
3. Season It is spring in northern hemisphere, and autumn in southern hemisphere during vernal equinox. It is spring in southern hemisphere, and autumn in northern hemisphere during autumnal equinox.
5. Write differences between Aphelion and Perihelion.
Ans. The differences between Aphelion and Perihelion are as follows-
Point of difference Aphelion Perihelion
1. Concept Average distance between Sun and Earth is maximum (152 million km) during aphelion. Average distance between Sun and Earth is minimum (147 million km) during perihelion.
2. Date It occurs on 4 July. It occurs on 3 January.
3. Speed of revolution Speed of revolution decreases in this time. Speed of revolution increases in this time
6. Scientists carry out expeditions to Antarctica in December. Give reasons to support your answer.
Ans. Scientists carry out expeditions to Antarctica in December because-
  1. Longer days: The apparent southward movement of the Sun in December makes days longer and nights shorter. Longer days make it easier to carry out experiments and research in Antarctica.
  2. Increase in temperature: The southern hemisphere experiences summer in December. The temperature in the coastal regions of Antarctica rise above the freezing point, making it easier for scientists to cope with the weather.
  3. Easier passage: Large chunks of ice in Antarctica melts in summer, thus allowing scientific explorers easier passage into the continent using ships.
7. Why are season changes not felt in the equatorial region?
Ans. Season changes are not felt in the equatorial region, i.e., the region around the Equator (0° latitude), due to the following reasons-
  1. Equal length of days and nights: The circle of illumination intersects the Equator at right angles; thus, length of days and nights are equal throughout the year in this region.
  2. Vertical rays of the Sun: The rays of the Sun fall vertically on the Equator almost throughout the year. Hence it remains warm all the year round.
  3. Convectional rainfall: The equatorial region experiences convectional rainfall for most of the year.
8. New Zealand celebrates Christmas in summer. State reasons to support your answer.
Ans. As the Earth revolves around the Sun, during November to January, the southern hemisphere remains tilted towards the Sun, while the northern hemisphere remains away from the Sun. Due to this, during these three months, the southern hemisphere experiences summer. Thus, 25 December, i.e., Christmas, is celebrated during summer in New Zealand, which lies in the southern hemisphere.
9. Why is Norway called ‘the land of midnight Sun’? lled the land of
Ans. The Sun is seen at night in Norway because the northern hemisphere of the Earth tilts towards the Sun from 21 March to 23 September. The North Pole and regions beyond the Arctic Circle experiences six months of continuous daylight when the Sun never sets. Thus the Sun is visible in the sky even at local time 12 o’clock in Norway and its adjacent areas. That is why, Norway is called ‘the land of midnight Sun’.
10. What is solar path or ecliptic?
Ans. The path followed by the Sun during its apparent movement around the Earth throughout the year is known as the solar path or ecliptic. This apparent movement of the Sun takes place between the Tropic of Cancer in the north and the Tropic of Capricorn in the south. From 21 June to 22 December, the Sun gradually shifts to the south. This is known as the apparent southward movement of the Sun. On 21 June, the Sun is vertically overhead the Tropic of Cancer, on 23 September and 21 March, it remains vertically overhead the Equator, and on 22 December, the Sun is vertically overhead the Tropic of Capricorn. From 22 December to 21 June, the Sun gradually shifts to the north. This is known as the apparent northward movement of the Sun. This path through which the Sun moves throughout the year is known as solar path or ecliptic.

Short Answer Type Questions

1. What is latitude?
Ans. The imaginary circular lines which run from west to east, on either side of the Equator, on the Earth’s surface are known as latitudes or parallels of latitude. The Equator is also one of the latitudes.
2. What is the Earth’s annual movement known as?
Ans. The Earth moves in its elliptical orbit around the Sun in 365 days. This movement is known as the annual movement of the Earth or Earth’s revolution. The revolution of the Earth is responsible for change of seasons and variation in the span of days and nights.
3. Which place on Earth has 6 months of daytime and 6 months of night?
Ans. From 21 March to 23 September the north polar regions experience 6 months of daytime and the south polar regions experience 6 months of night during this period. From 23 September to 21 March, the opposite is noticed in both these areas.
4. Which place on Earth experiences no change of seasons?
Ans. The equatorial region experiences no change of season all the year round. This region receives straight rays of the Sun throughout year round and hence has a hot climate.
5. What is meant by the Sun’s apparent northward movement?
Ans. From 22 December to 21 June, the Sun apparently moves northward, from Tropic of Capricorn (23½°S) towards Tropic of Cancer (23½°N). This is known as Sun’s apparent northward movement.
6. What is known as the sun’s apparent southward movement?
Ans. From 21 June to 22 December, the Sun apparently moves southward from the Tropic of Cancer (23½°N) towards the Tropic of Capricorn (23½°S). This is known as the Sun’s apparent southward movement.
7. What is the position of Earth during Aphelion?
Ans. The Earth is the farthest from the Sun during Aphelion. This phenomena occurs on 4 July. During this period the distance between the Earth and the Sun is approximately 152 million km.
8. What is the position of the Earth during Perihelion?
Ans. The Earth is the closest to the Sun during Perihelion. This phenomena occurs on 3 January. During this phenomena, the distance between the Earth and the Sun is approximately 147 million km.
9. What is the Earth’s orbital plane?
Ans. The plane along the Earth’s orbit is known as the Earth’s orbital plane. If the points on the elliptical orbit of the Earth are connected via a straight line to their diagonally opposite points, then this plane is obtained.
10. What is season cycle?
Ans. The change of the four main seasons on the Earth (summer, monsoon, autumn and spring) in a cyclical pattern is known as season cycle.
11. What is summer solstice?
Ans. On 21 June, the rays of the Sun fall vertically on the Tropic of Cancer (23 ½%2°N). On this day, the day is the longest and night is the shortest in the northern hemisphere. This day is known as the summer solstice.
12. What is winter solstice?
Ans. On 22 December, the rays of the Sun fall vertically on the Tropic of Capricorn (23½°S). On this day the day is the longest and night is the shortest in the southern hemisphere. This day is known as winter solstice.
13. What is autumnal equinox?
Ans. On 23 September, the Earth’s position on its orbit is such that the rays of the Sun fall directly on the Equator. This is responsible for making the duration of days and nights equal in both the hemispheres. Due to the prevalence of autumn season in the northern hemisphere during this time, this day is called autumnal equinox.
14. What is vernal equinox?
Ans. On 21 March, the Earth’s position on its orbit is such a way that the rays of the Sun fall directly on the Equator. This makes the duration of days and nights equal in both the hemispheres. Since it is spring season in the northern hemisphere during this period, this day is known as vernal equinox.
15. What is aurora?
Ans. When there is 6 months of darkness in the polar regions (north or south), sometimes streaks of light resembling rainbows are observed in the sky. These are known as aurora.
16. What is aurora borealis?
Ans. The streaks of light resembling rainbows, observed in the sky during the 6 months of darkness in the north polar region (23 September to 21 March) is known as aurora borealis.
17. What is aurora australis?
Ans. The streaks of light resembling rainbows, which are observed in the sky during the 6 months of continued darkness in the south polar region (21 March to 23 September) is known as aurora australis.
18. What are the effects of the revolution of the Earth?
Ans. The effects of the revolution of the Earth are- (1) change of years, (2) change in duration of days and nights, (3) change of seasons, (4) change in position of the stars.
19. What is ecliptic?
Ans. The path of the apparent annual movement of the Sun is known as ecliptic. During the year, the sun’s rays move from falling directly on the Tropic of Cancer to the Tropic of Capricorn and vice versa.
20. What are the factors responsible for change of seasons?
Ans. The factors responsible for change of seasons are- (1) the Earth’s revolution, (2) the tilted placement of the Earth on its Axis, (3) the difference in angle of the rays of the Sun.
21. What is ‘midnight Sun’?
Ans. When the Sun is seen in the midnight sky it is known as ‘midnight Sun’. Midnight Sun is seen in areas of the north polar region from 21 March to 23 September.
22. What is solar year?
Ans. While rotating on its axis, the Earth completes one revolution around the Sun along its orbit in 365 days 5 hours 48 minutes 46 seconds. This is known as solar year.
23. What is the ‘midday Sun’?
Ans. When the rays of the Sun fall vertically on a line of longitude, it is known as ‘midday Sun’ of that longitude.
24. What is an orbit?
Ans. An imaginary path along which the Earth moves around the Sun is known as orbit of the Earth. Shape of the Earth’s orbit is elliptical.
25. Where is the Sun with respect to the Earth’s orbit?
Ans. The Earth’s orbit is elliptical in shape and the Sun is located at the focus with respect to the Earth’s orbit. Therefore, distances between the Earth & the Sun are not same all the time.
26. What do you mean by ‘Land of midnight Sun’?
Ans. When the Arctic region has day for about six months at a stretch from 21 March to 23 September, the Sun can be seen even at night from Hammerfest, located in the northern part of Norway (70° north latitude). Thus Hammerfest is known as the ‘Land of midnight Sun’.

Multiple Choice Type Questions [MCQ type]

Write the correct answer from the given alternatives

1. The date on which Earth is at Perihelion position is-
A. 3 January
B. 4 January
C. 21 March
D. 23 September
Ans. A
2. The country called ‘the land of the midnight Sun’ is-
A. Australia
B. Norway
C. Japan
D. Sri Lanka
Ans. B
3. The Tropic of Cancer receives direct rays of the Sun on-
A. 21 March
B. 21 June
C. 21 July
D.21 December
Ans. B
4. Autumnal equinox occurs on-
A. 23 June
B. 23 August
C. 23 September
D. 23 November
Ans. C
5. The Earth completes one revolution around the Sun in-
A. 364 days
B. 360 days
C. 365 days
D. 367 days
Ans. C
6. Summer in Antarctica starts in-
A. June
B. July
C. December
D. September
Ans. C
7. The aurora borealis can be seen at the-
A. equatorial region
B. north polar region
C. south polar region
D. middle latitudes
Ans. B
8. The shape of the Earth’s orbit is-
A. circular
B. elliptical
C. triangular
D. semicircular
Ans. B
9. The Earth’s movement around the Sun is called-
A. apparent motion
B. rotation
C. revolution
D. daily motion
Ans. C
10. The sun’s apparent northward movement ends on-
A. 22 July
B. 21 July
C. 21 June
D. 21 March
Ans. C
11. The Earth experiences equal duration of days and nights on-
A. 21 March and 21 June
B. 21 March and 23 September
C. 22 July and 22 December
D. 23 September and 4 July
Ans. B
12. The speed of the Earth’s revolution is about-
A. 20 km/s
B. 30 km/s
C. 40 km/s
D. 50 km/s
Ans. B
13. Aphelion occurs on-
A. 4 July
B. 3 January
C. 2 February
D. 1 March
Ans. A
14. At Perihelion, the distance between the Sun and the Earth is-
A. 150 million km
B. 140 million km
C. 152 million km
D. 147 million km
Ans. D
15. At Aphelion, the distance between the Sun and the Earth is-
A. 150 million km
B. 140 million km
C. 152 million km
D. 147 million km
Ans. C
16. Change of seasons does not occur in the-
A. equatorial region
B. tropical region
C. sub-tropical region
D. polar region
Ans. A
17. The Sun appears larger in the northern hemisphere in-
A. summer
B. autumn
C. winter
D. spring
Ans. C
18. The longest night of the northern hemisphere occurs on-
A. 21 March
B. 23 September
C. 21 July
D. 22 December
Ans. D
19. The longest day and the shortest night in the southern hemisphere occurs on-
A. 21 March
B. 23 September
C. 21 July
D. 22 December
Ans. D
20. The average distance of the Earth from the Sun is-
A. 147 million km
B. 150 million km
C. 152 million km
D. 160 million km
Ans. B

Very Short Answer Type Questions

Fill in the blanks with suitable words

1. The distance between the Earth and the Sun is least during …………
Ans. Perihelion
2. …………. occurs on 21 March.
Ans. vernal equinox
3. Winter solstice occurs on ………….
Ans. 22 December
4. ……….. means equal length of day and night.
Ans. Equinox
5. Norway is called the ‘Land of the …………. Sun’.
Ans. midnight
6. The Sun is located at the ……….. of the elliptical orbit of the Earth.
Ans. focus
7. During revolution, the ………… pole faces the Pole Star. 
Ans. North
8. There is no change of seasons at the ………… region.
Ans. equatorial
9. Leap year occurs every …………. years.
Ans. four
10. The Earth’s orbit is …………. in shape. 
Ans. elliptical
11. The speed of revolution of the Earth is ………… per hour.
Ans. 107200 km
12. The first scientist to say that all planets have an elliptical orbit was …………
Ans. Copernicus
13. The ………….. region does not experience change of seasons.
Ans. equatorial
14. While it is summer in the northern hemisphere the southern hemisphere experiences ………….
Ans. winter
15. Change of season occurs due to …………. movement of the Earth.
Ans. revolutional
16. There are ………… days in the month of February in a leap year. 
Ans. 29

If the statement is true, write ‘T’ and if false, write ‘F against the following

1. The cycle of seasons in the southern hemisphere is opposite to that in the northern hemisphere.
Ans. T
2. The Earth is farthest from the Sun on 21 September.
Ans. F
3. The year 2016 was not a leap year.
Ans. F
4. The Earth has an elliptical orbit.
Ans. T
5. The polar regions experiences cold climate almost throughout the year.
Ans. T
6. The equatorial regions receive the direct rays of the Sun throughout the year.
Ans. T
7. During the winter season in the northern hemisphere, the Earth revolves faster.
Ans. T
8. The days are longer in the northern hemisphere during the month of December.
Ans. F
9. The polar regions experience 6 months of night.
Ans. T
10. The Sun is farther away from us during the winter season.
Ans. F
11. 22 December is the longest day of the southern hemisphere.
Ans. T
12. It is spring on 21 March all over the Earth.
Ans. F
13. Winter solsctice is on 21 July.
Ans. F
14. Expedition to Antarctica is suitable in December.
Ans. T
15. Earth rotates 360° on its axis in 24 hours.
Ans. F
16. The Sun appears bigger during DecemberJanuary due to perihelion position of the Earth.
Ans. T

Answer in one or two words

1. What is the path of the Sun’s apparent annual movement called?
Ans. Ecliptic.
2. On which day does the autumnal equinox, occur?
Ans. 23 September.
3. On which day does winter solstice take place?
Ans. 22 December.
4. Which region of the Earth experiences six months of night?
Ans. The polar region.
5. On which date does the northern hemisphere experience its longest day?
Ans. 21 June.
6. Where can we see Aurora australis?
Ans. South Pole.
7. During Aphelion, how does the Sun look in the southern hemisphere in winter compared to that in summer?
Ans. Smaller.
8. On which day is the Earth closest to the Sun? 
Ans.  3 January.
9. Which place experiences 24 hours of daytime on 21 June?
Ans. North Pole.
10. “The Earth has a revolutionary motion also.”-Who first proved this statement?
Ans. Nicolaus Copernicus.

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