Chapter 29, Problem 21A

Is daytime a bit longer or is it a bit shorter because of atmospheric refraction?

To determine

To Explain: The effect of refraction on the day time.

Explanation of Solution

Introduction:

The light deviates from a straight line path as it passes through the atmosphere due to variation in the density of air. This phenomenon is known as atmospheric refraction.

Explanation: 

Due to the atmospheric refraction, there are various phenomena which occur such as rainbows, mirages, sundogs, etc.

When the light enters from one medium to another at $90°$ , it does not refract. But when light enters into the earth’s atmosphere, it refracts multiple times due to the variation of density of atmosphere. Due to the effect of refraction, the day light is not exactly 12 hours. It is slightly longer than night time by approximately 4 minutes.

Conclusion: 

A day time is 4 minutes longer than the night time due to atmospheric refraction.