Explain why, the sun can be seen about two minutes before actual sunrise. Draw a diagram to illustrate your answer.
Because of atmospheric refraction of sun's light the sun can be seen about two minutes before actual sunrise. When the sun is slightly below the horizon, then the sun's light coming from less dense air to more dense air is refracted downwards as it passes through the atmosphere and the appears to be raised above the horizon.
Let us see a diagram to illustrate it:-