What is atmospheric refraction? Use this phenomenon to explain the following natural events:

a) Twinkling of stars
b) Advanced sunrise and delayed sunset

Draw diagrams to illustrate your answer.

Atmospheric refraction is the refraction of light caused by the earth's atmosphere due to change in the refractive indices of different layers of the atmosphere.
a) Twinkling of stars: Stars are distant point sourced sources of light. The path of the rays of light comig f=coming from the distant star goes on varying due to atmospheric refraction slightly. Thus, apparent position of the star fluctuates and the amount of star light entering the eye flickers giving the twinkling effect.

b) Advanced sunrise: When the sun is slightly below the horizon, light rays coming from the sun travel from rarer to denser layers of air. As a result of the atmospheric refraction of light. light appears to come from a higher position above the horizon. Therefore, the sun appears earlier than actual sunrise.
Delayed sunset: During sunset, the apparent position of the sun is visible to us and not the actual position due to the same bending of light rays effect. Therefore, because of refraction, we see the sunset afterwards although it has actually moved from its position.