1. Answer the following questions briefly.
(a) What is the angle of inclination of the earth’s axis with its orbital plane?
Answer– The axis of the earth which is an imaginary line, makes an angle of 66½° with its orbital plane.
(b) Define rotation and revolution?
Answer– Rotation- Rotation is the movement of the earth on its axis. Revolution- The movement of the earth around the sun in a fixed path or orbit is called revolution.
(c) What is a leap year?
Answer– Every fourth year, February is of 29 days instead of 28 days. Such a year with 366 days is called a leap year.
(d) Differentiate between the Summer and Winter solstice.
Answer– Summer Solstice –
(1) Summer solstice falls on 21st June.
(2) Longest day and Shortest night in northern Hemisphere.
(3) Summer season in the northern hemisphere. (4) winter in the southern hemisphere.
(1) it falls on 22nd December
(2) Longest day and shortest night in southern hemisphere (3) summer season in the southern hemisphere. (4) winter in the northern hemisphere.
(e) What is an equinox?
Answer– On 21st March and September 23rd, direct rays of the sun fall on the equator. At this position, neither of the poles is tilted towards the sun so the whole earth experiences equal days and nights. This is called an equinox.
(f) Why does the Southern Hemisphere experience Winter and Summer Solstice at different times than that of the Northern Hemisphere?
Answer– This happens because of the angle of inclination of the earth’s axis with its orbital plane. On 21st June, the sunlight falls directly on the Tropic of Cancer. Hence, it is the summer solstice in the northern hemisphere. On 22nd December, the sunlight falls directly on the Tropic of Capricorn. Hence, it is the summer solstice in the southern hemisphere.
(g) Why do the poles experience about six months day and six months night?
Answer– The poles experience 6 months day and 6 months nights due to the tilt of the earth on its own axis. Because of this tilt, each pole is tilted towards and away from the earth for about 6 months each.
2. Tick the correct answer.
(a) The movement of the earth around the sun is known as
(i) Rotation (ii) Revolution (iii) Inclination
Answer: (ii) Revolution
(b) Direct rays of the sun fall on the equator on
(i) 21 March (ii) 21 June (iii) 22 December
Answer: (i) 21 March
(c) Christmas is celebrated in summer in
(i) Japan (ii) India (iii) Australia
Answer: (iii) Australia
(d) Cycle of the seasons is caused due to
(i) Rotation (ii) Revolution (iii) Gravitation
Answer: (ii) Revolution
3. Fill in the blanks:
(a) A leap year has ____________ number of days.
Answer: A leap year has 366 number of days.
(b) The daily motion of the earth is _____________.
Answer: The daily motion of the earth is rotation.
(c) The earth travels around the sun in ______________ orbit.
Answer: The earth travels around the sun in an elliptical orbit.
(d) The sun’s rays fall vertically on the Tropic of _____________ on 21st June.
Answer: The sun’s rays fall vertically on the Tropic of Cancer on 21st June.
(e) Days are shorter during _______________ season.
Answer: Days are shorter during the winter season.