Q: Answer the following questions briefly:
a) What is the angle of inclination of the earth’s axis with its orbital plane ?
Ans: The angle of inclination of the earth’s axis with its orbital plane is 23.5 degree.
b) Define rotation and revolution.
Ans: Rotation – Rotation is the movement of the earth on its axis.
Revolution – The movement of earth around the sun in a fixed path or orbit is called Revolution.
c) What is a leap year ?
Ans: Earth takes 365 and 1/4 days to revolve around the sun. We consider a year as consisting of 365 days only and ignore six hours for the sake of inconvenience. Six hours saved every year are added to make one day (24 hours) over a span of four years. This surplus day is added to the month of February. Thus every fourth year, February has 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.
|Summer Solstice||Winter Solstice|
|It occurs on 21st June.||It occurs on 22nd December.|
|On this day, Northern hemisphere is tilted towards the sun. The sun rays fall directly on Tropic of Cancer. As a result, these areas receive more.||On this day, Southern Hemisphere is tilted towards the sun. The sun rays fall directly on Tropic of Capricorn. As a result, these areas receive more heat.|
|In Northern hemisphere, day is longer than night on this day while in Southern hemisphere night is longer than day||In Southern hemisphere, day is longer than night on this day while in Northern hemisphere night is longer than day.|
e) What is an equinox ?
Ans: On 21st March and 23rd September, direct rays of the sun fall on the equator. At this position, neither the poles is tilted towards the sun; so the whole earth experiences equal days and equal nights. This is called an equinox.
f) Why does the Southern Hemisphere experience Winter and Summer Solstice in different times than that of the Northern Hemisphere ?
Ans: The Earth has two hemispheres. The hemisphere which faces the sun experiences summer and the other part experiences winter. Thus, the Southern hemisphere Winter and Summer in different times than that of the Northern hemisphere.
g) Why do the poles experience about six months day and six months night ?
Ans: The poles experiences about six months day and six months night due to the inclination of earth’s axis.