1. Answer the following questions briefly.
(a) What is the angle of inclination of the earth’s axis with its orbital plane?
Answer.
- The angle of inclination of the Earth's axis with its orbital plane is 66.5°
(b) Define rotation and revolution.
Answer.
- The movement of the Earth around its axis is called rotation; It takes 24 hours to rotate once. The period of one rotation is also called an Earth day.
- The movement of the earth in an elongated path around the sun is called revolution; It takes 365.25 days to make one revolution.
(c) What is a leap year?
Answer.
- The motion of the Earth's revolution around the Sun is called revolution. It takes 365.25 days or 365 days and 6 hours for the earth to make one revolution which we call a year.
- For convenience, we assume 365 days in a year and save six hours every year to make one day once in four years (6 * 4 = 24 hours). Therefore, every 4 years there comes a year of 366 days, which we call leap year.
- The month of February in a leap year is of 29 days.
(d) Differentiate between the Summer and Winter Solstice.
Answer.
The following are differences between summer and winter solstice:
The day( 21 June) when the northern hemisphere is closest to Sun is called Summer Solstice whereas the day( 22 December) in which the southern hemisphere is closest to Sun is called Winter Solstice.
In summer Solstices, the northern hemisphere gets maximum heat and experience the longest day and shortest night whereas the southern hemisphere gets the lowest heat and experienced the longest night and shortest day.
In Winter Solstices, the northern hemisphere gets the lowest heat and experienced the longest night and shortest day whereas the southern hemisphere gets maximum heat and experience the longest day and shortest night.
(e) What is an equinox?
Answer.
- When the whole earth experienced equal day and night, it is called an equinox.
- This occurs when the sun's rays fall directly on the Earth's equator.
- The equinox falls twice a year on March 21 and September 23.
(f) Why does the Southern Hemisphere experience Winter and Summer Solstice in different times than that of the Northern Hemisphere?
Answer.
The Earth revolves around the Sun in an inclined axis, so when the Northern Hemisphere tilts towards the Sun, at the same time the Southern Hemisphere turns away from the Sun, that is why both the hemisphere experiences winter and summer solstice at a different time.
(g) Why do the poles experience about six months day and six months night?
Answer.
- There are about six months of day and six months of the night at the poles, this happens due to the rotation and revolution of the earth on its axis with an inclination of 23.5 degrees.
- In the revolution of the Earth, the Northern Hemisphere is towards the Sun for 6 months, then the North Pole has days for 6 months, the South Pole has nights for 6 months, and the next 6 months when the South Hemisphere is towards the Sun, then the North Pole experienced nights for 6 months and day for 6 months in the Southern Hemisphere.
2. Tick the correct answers.
(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 ____366___________ number of days.
(b) The daily motion of the earth is _____24 hours__________.
(c) The earth travels around the sun in _______fixed__elongated(ellipitical)_____ 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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