What is atmospheric refraction? Use this phenomenon to explain the advanced sunrise and delayed sunset.

Hint: When light passes from one medium to another it undergoes refraction. Since the atmosphere contains different layers of air with different density, light will suffer refraction as it passes through the atmosphere. Using this we can explain the reason for advanced sunrise and delayed sunset.

Complete step by step answer:
When light travels from one medium to another the path of the light changes. This is known as refraction of light. We know that the atmosphere contains several layers of air having different densities. When light travels through these layers it will suffer refraction. This is known as atmospheric refraction.

The advanced sunrise and delayed sunset can be explained with the help of atmospheric refraction.

We know that the atmosphere contains several layers of air with varying density. The layers closer to the surface of earth are comparatively denser than the layers above. There is a gradual increase in density as we move from top layers towards the bottom. During the time of sunrise when the sun is below the horizon the light from the Sun travels through successively denser layers. When a ray of light passes from a rarer medium to denser medium it will bend towards the normal. Hence the sunlight will get deviated more and more towards the normal as it passes through the layers of atmosphere until it falls upon the eyes of the observer. Thus, the observer will feel that the rays are coming from the sun above the horizon. This is how we are able to see the sun before it actually rises above the horizon. For the same reason we will see the sun for some more time even after it has gone below the horizon during the time of sunset. The difference in time is only about two minutes.

Note: Remember that when a ray of light passes from rarer medium to a denser medium it will bend towards the normal. When a Ray of light passes from denser medium to rarer medium, the ray will bend away from the normal. Since the lower layers of the atmosphere are denser, the sunlight bends towards the normal as it passes through the atmosphere.