Atmospheric refraction causes advance sunrise and delayed sunset. By how much time is:(a) sunrise advanced?(b) sunset delayed?

(a) Sunrise is advanced by about two minutes.

(b) Sunset is delayed by about two minutes.

Explanation

Due to the refraction of sunlight caused by the atmosphere, we can see the sun 2 minutes before it's actually above the horizon (advanced sunrise), and 2 minutes even after the actual sunset (delayed sunset).

This happens because when the sun is slightly below the horizon, then the sun's light coming from the less dense air to more dense air is refracted downwards as it passes through the atmosphere. Thus, due to this atmospheric refraction, the sun appears to be raised above the horizon when actually it is slightly below the horizon.