Question

Twinkling of stars is due to:
A. Variation of refractive index in the earth’s atmosphere.
B. The fact that light is not emitted by the stars continuously.
C. The absorption of light by earth’s atmosphere.
D. None of these.

Answer 1

Hint: Earth has its own atmosphere which has different layers, each layer has its significance. Due to this atmospheric layer we experience phenomena like scattering, reflection, refraction, radiation etc. Similarly there is a phenomenon known as atmospheric refraction which takes place due to change in density of air.

Complete step-by-step answer:
When the light from stars enters earth’s atmosphere it goes through the phenomenon known as refraction as the earth’s atmosphere has varying temperature and density. The density of air changes continuously resulting in continuous variation in the refractive index. When the light travels in a denser medium, it bends towards normal, that is the angle to refraction is less and hence refractive index greater.
Hence, the stars twinkle due to the variation of the refractive index of earth’s atmosphere.

So, the correct answer is “Option A”.

Additional Information: Refraction is the phenomenon in which light travels from one medium to the other medium and while doing so it either bends towards the normal line or away from the normal lines.
It is due to refraction only that we see the sun before sunrise or sunset, that is when the sun is at the horizon.

Note: The planets although don't twinkle because they don’t have their own light and they reflect the light instead and also they are near to us in comparison to the light that is not refracted that much. Same way, the sun is also a star but as we are really close enough to it as compared to others we can see the sun without twinkling.