Wt is atmospheric refraction & why is it caused?

1.	Wt is atmospheric refraction & why is it caused?
Answer» The density of air is higher near the surface of the earth. As we move upwards from the surface of the earth, density of air keeps on decreasing. This increase in density as light rays come towards earth is the cause of refraction.Some consequences of atmospheric refraction are:1. Twinkling of stars.2. The stars seem higher than they actually are.3. Advance sunrise and delayed sunset.

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