Question 1 Answer the following questions briefly.
(a) What is the angle of inclination of the earth’s axis with its orbital plane?
(b) Define rotation and revolution.
(c) What is a leap year?
(d) Differentiate between the Summer and Winter Solstice.
(e) What is an equinox?
(f) Why does the Southern Hemisphere experience Winter and Summer Solstice in different times than that of the Northern Hemisphere?
(g) Why do the poles experience about six months day and six months night?
Answer
(a) The angle of inclination of the earth’s axis with its orbital plane is 66°
(b) The movement of the earth on its axis is known as rotation. The movement of the earth around the sun in a fixed path or orbit is known as revolution.
(c) The year in which February is of 29 days instead of 28 days is called a leap year. Thus a leap year is of 366 days instead of 365 days.
(d) Summer Solstice : The position of the Earth on 21st June when there is summer in Northern Hemisphere regions and reverse conditions i.e. winter in Southern Hemisphere. This position of the Earth is called summer Solstice.
Winter Solstice: The position of the Earth on 22nd December when there is Summer in Southern Hemisphere regions and reverse conditions i.e. winter in Northern Hemisphere. This position of the Earth is called winter Solstice.
(e) When the whole Earth experience equal day and night , it is called equinox. There are two such days i.e. 21st march and 23rd September. On 21st March in the Northern hemisphere, this position is the spring equinox. Autumn equinox is in the Southern hemisphere. In the Northern hemisphere on 23rd September the position of the Earth is Autumn equinox and in the Southern hemisphere, it is the Spring equinox.
(f) The Earth is spherical in shape and keeps on revolving and is divided into two hemisphere. When Southern hemisphere gets in front of the Sun , the portion facing the Sun experiences summer while the other half away from the Sun experiences winter and vice versa.
The southern hemisphere is tilted towards the Sun on 22nd December, hence summer solstice is there in the Southern hemisphere. At that time winter solstice is in the Northern hemisphere when it is away from the Sun. On the contrary, on 21 June the Northern hemisphere is tilted towards the Sun. Hence summer solstice is in the Northern hemisphere and winter solstice is in the Southern hemisphere.
(g) The poles experience six months day and six months night because of the following reasons:
(1) When the Northern hemisphere is tilted towards the Sun, the North Pole remains in the light for the whole of the day (24 hours). This position remains for six months (from 21st March to 23rd September).
(2) On the contrary in the Southern hemisphere, the South Pole does not get light during these six months. Hence it experiences night for six months (from 23rd September to 21st March).
(3) When the Southern hemisphere is tilted towards the sun, the South Pole remains in light for 24 hours for six months from 23rd September to 21st March. The reverse is the conditions at the North Pole-six months’ night.
Question 2 Tick the correct answers.
(a) The movement of the earth around the sun is known as
(i) Rotation (ii) Revolution (iii) Inclination
(b) Direct rays of the sun fall on the equator on
(i) 21 March (ii) 21 June (iii) 22 December
(c) Christmas is celebrated in summer in
(i) Japan (ii) India (iii) Australia
(d) Cycle of the seasons is caused due to
(i) Rotation (ii) Revolution (iii) Gravitation
Answer
(a) Revolution
(b) 21 March
(c) Australia
(d) Revolution
Question 3 Fill in the blanks.
(a) A leap year has ___________ number of days.
(b) The daily motion of the earth is___________.
(c) The earth travels around the sun in ___________ orbit.
(d) The sun’s rays fall vertically on the Tropic of ___________ on 21st June.
(e) Days are shorter during ___________ season.
Answer
(a) A leap year has 366 number of days.
(b) The daily motion of the earth is rotation.
(c) The earth travels around the sun in elliptical orbit.
(d) The sun’s rays fall vertically on the Tropic of Cancer on 21st June.
(e) Days are shorter during winter season.
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