Assertion (A): The speed of revolution of the earth is uniform.

Reason (R): When the earth is closer to the sun, the gravitational pull makes the earth move faster than when it is away from the sun.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R does not explain A.
3. A is true but R is false.
4. A is false but R is true.

Solstice : Summer/Winter :: ……………. : Spring/Autumn

1. Solstice
2. Equinox
3. Vernal
4. None of the above.

The period of diffused light between sunset and complete darkness is called ……………. .

1. dawn
2. dusk
3. twilight
4. Both (2) and (3)

The duration of twilight :

1. increases to the poles
2. might last for as much as 7 weeks at the poles
3. is as long as the sun is 18° below the horizon
4. all of the above.