Question

What is atmospheric refraction? Use this phenomenon to explain the following natural events.
i) Twinkling of stars
ii) Advanced sunrise and delayed sunset.

Answer 1

$\huge \bf{Atmospheric \: Refraction.}$

The density of the atmosphere, as we know goes on decreasing as the distance above the sea level increases. Hence, the refractive index of a layer of air at a particular level goes on changing. Due to this refraction takes place when light passes through the earth's atmosphere. This phenomenon is called as atmospheric refraction.

$\huge \mathtt \red{Twinkling \: of \: Stars.}$

It is due to atmospheric refraction of star light. The density of the atmosphere goes on decreasing as the distance above the sea level increases.

Thus, the refractive index of a layer of air at a particular level goes on changing. Due to these variations in the refractive indices of the various layers of air, the light from a star passing through the atmosphere changes its path from time to time and therefore the amount of light reaching the eye is not always the same. This increase or decrease in the intensity of light reaching the eye results in the change in apperant position of the star. Hence, the stars appear to be twinkling.

$\huge \mathtt \red{Advanced \: sunrise \: and \: delayed \: sunset.}$

The advanced sunrise and delayed sunset is because of atmospheric refraction.

Answer 2

Twinkling of stars: Stars twinkle on account of atmospheric refraction. Starlight undergoes refraction many times before reaching the earth. It occurs because there is a gradual increase in the refractive index from the atmosphere to the earth's surface...