Question

How does refraction take place in the atmosphere? Why do stars twinkle but not the planets?

Answer 1

Refraction in atmosphere

1. When light travels from one medium to another medium, its velocity in the medium change, which causes it to change its direction of propagation.
2. This phenomenon is called the refraction of light.
3. There are several layers in our atmosphere, where the optical density increases as one approaches the earth.
4. Hence, when refraction occurs due to passing through the several layers in our atmosphere, light tends to bend towards the normal as it passes through the denser layers.

Twinkling of stars

1. Due to the great distance between us and the stars, the light coming from it suffers multiple refractions.
2. The result of these numerous amounts of refractions causes twinkling.
3. On the other hand, planets are much closer to us than the stars.
4. Hence they do not undergo so many multiple refractions as compared to stars.
5. Therefore, planets do not seem to twinkle.