Question

Assertion (A): Stars twinkle, while planets shine steadily.
Reason (R): Stars have their own light where as planet do not.

• A. Both A and R are true and R is the correct explanation of A
• B. Both A and R are true but R is not the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Answer 1

The correct option is B Both A and R are true but R is not the correct explanation of A

As the stars have their own light, and are very much far away from us, the light coming from the stars has to travel a very long distance. So, stars seems like a point source where as planets are closer to Earth and so appear as tiny disks in our sky.
Light from the stars bent many times and in random directions due to Earth's atmosphere. This random refraction results in the star winking out - twinkling.
Planets are closer to Earth and so appear as tiny disks in our sky. The light from these little disks is also refracted by Earth’s atmosphere, as it travels toward our eyes. Due to the planets’ apparent closeness to Earth, the light coming from these celestial bodies does not bend much due to Earth’s atmosphere. Also not beinga point source but appearing as disks, they comprise of several point sources- lights of which are coming at the same time. So a deviation in light path of one point source can cancel with deviations of other and would average out to give rise to a steady shine. Therefore, the light coming from our solar system’s planets does not appear to twinkle like stars.