Explain with the help of a diagram, how we are able to observe the sunrise about two minutes before the sun gets above the horizon. Hence, explain why does apparent duration of a day from sunrise to sunset is 4 minutes more than its actual duration.

Explain with the help of a diagram, how we are able to observe the sun

1.	Explain with the help of a diagram, how we are able to observe the sunrise about two minutes before the sun gets above the horizon. Hence, explain why does apparent duration of a day from sunrise to sunset is 4 minutes more than its actual duration.
Answer» Solution :The air becomes rarer as its height above the earth increases. Its refractive INDEX decreases. A ray of LIGHT from the Sun when it enters the atmosphere at the horizon gets refracted from a rarer to a DENSER medium. The rays, therefore gradually bend towards the normal and the Sun appears to be raised. As a result, the Sun is visible to an observer nearly two minutes before actual sunrise at the horizon. Similarly, even after actual sunset, Sun is seen by us for about 2 minutes. Thus, in EFFECT Sun is seen for 4 minutes more. It means that apparent duration of day (from sunrise to sunset) has increased by 4 minutes than its actual duration.