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 ½â—¦.
(b) Rotation:
- The movement of the Earth on its axis is called rotation.
- The Earth takes 24 hours to complete one rotation.
- Days and nights are caused due to rotation of the Earth.
Revolution:
- The movement of the Earth around the sun in a fixed path or the orbit is called revolution.
- The Earth takes 365 days six hours to complete one revolution.
- Seasons are caused due to revolution of the Earth.
(c) A year with 366 days is called leap year. It occurs once in four years on the month of February and it is 29th day of that month. It is also called intercalary year. The Earth do not take exact 365 days in an year and 24 hours in a day, so we add them as one extra day once in four year.
(d) Differences between summer and winter solstice are as follows:
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Summer Solstice
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Winter Solstice
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Summer solstice occurs on 21st June in Northern Hemisphere.
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Winter Solstice occurs on 22nd December in Southern Hemisphere.
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The Northern Hemisphere experiences more heat and light.
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Southern Hemisphere experiences less heat and light.
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It is summer in Northern Hemisphere.
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It is winter in Southern Hemisphere.
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Days are longer and nights are shorter.
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Nights are longer and days are shorter.
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(e) On 23rd September and 21st March, the rays of sun directly falls on the equator. So, at that position neither of the poles are tilted. So at that specific or we can say a particular day the earth experiences equal days and nights and this is called as equinox.
(f) The Southern Hemisphere experience winter and summers solstice in different times than that of the Northern Hemisphere because:
- Southern Hemisphere is tilted towards the Sun on 22nd December, so summer Solstice is there in Southern Hemisphere. At that time Winter Solstice is in Northern Hemisphere.
- In 21st June the Northern Hemisphere is tilted towards the Sun, so Summer Solstice is there and Winter Solstice is in the Southern Hemisphere.
(g) The poles experiences about six months day and six months night because:
- When Northern Hemisphere is tilted towards the Sun, The North Pole remains in the light for the whole day. This position remains for six months from 21st March- 23rd September.
- On the same time Southern Hemisphere is away from the Sun, the South Pole does not get light for six months. So it experiences night for six months and vice versa.
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