Page 2 - Lesson note atmospheric refraction

The light from stars is refracted as it comes down into earth’s atmosphere. The air
higher up in the sky is rarer and near the earth’s surface is denser. As the star light
falls down the dense air bends it more and thus stars appear higher than they
actually are.

3) Advance sunrise and delayed sunset
It is due to refraction of light that we are able to see the sun two minutes before
sunrise and two minutes after actual sunset. At the time of sunrise the sunlight is
coming from less dense air to more dense air. In this case the sunlight is refracted
downwards and because of this sun appears to be raised above the horizon than it
actually is.

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