NCERT 6th Class (CBSE) Social Science: Rotation and Revolution

Question: How are days and nights caused?

Due to the spherical shape of the earth, only one of it gets light from the sun at a time and the other half remains in darkness.

Question: Explain the phenomenon of the seasons with the help of a diagram.

Answer: (i) Summer solstice (21 June):

1. The north pole is inclined towards the sun, while the south pole is turned away from the sun.
2. The sun rays fall vertically fall over the tropic of Cancer (23 1/2°)
3. The large portion of the northern hemisphere gets heat and light from the sun.
4. Days are longer than night in the northern hemisphere.
5. The place in the northern hemisphere experience summer summer season.
6. The longest day and the shortest night occur on 21st June in northern hemisphere.
7. All the above conditions are reversed in the southern hemisphere.

(ii) Winter solstice (22nd December):

1. The south pole is inclined towards the sun, while the north pole is turned away from the sun.
2. The rays of the sun fall vertically over the tropic of the Capricorn (23 1/2° S).
3. The large portion of southern hemisphere receives heat and light from the sun.
4. Days are longer than night is the southerns hemisphere.
5. Places in the southern hemisphere experiences summer.
6. The longest day and shortest night occurs on 22nd December in the southern hemisphere.
7. All the above conditions are reversed in the northern hemisphere.

(iii) Spring and Autumnal Equinoxes (21 march and 23 September):

1. On 21 March and 23 September, the rays of the sun fall vertically on the equator.
2. The North Pole and the South Pole lie at an equal distance from the sun.
3. Days and night are equal duration throughout the world.
4. It is neither very hot nor very cold in the earth the hemispheres.
5. The Northern Hemisphere experiences spring season from 21 March and autumn season from 23 September. It is reverse in the Southern Hemisphere.
6. The equinoxes coincide with time of sunrise at one pole and the time of sunset at the other pole.
7. 21 March coincides with the New Year Day of the Indian National Calendar.