Explain why, the sun can be seen about two minutes before actual sunrise. Draw a diagram to Illustrate your answer.

light coming from the vacuum of space to the denser air of the earth's atmosphere is refracted downwards. Due to this refraction, the sun appears to be raised above the horizon even though it is slightly below the horizon.

In the figure below, the actual position of the sun is just below the horizon, but it appears to be just above the horizon, due to the atmospheric refraction. Thus, the sun appears to rise two minutes before the actual sunrise.