Question

explain that we can see the sun even what it is little below the horizon

Answer 1

Thanks for your query.
It's all about refraction.Not only we observe advanced sunrise but also delayed sunset.This is because when light enters from vacuum to earth's atmosphere,it basically enters from rarer to denser medium and bends towards horizon.During sunrise, when the sun is just below the horizon, our atmosphere causes the light rays to bend and we see the sun early. Similarly, at sunset, the apparent position of the sun is visible to us and not the actual position due to the same bending of light rays effect.

Answer 2

We can see the sun two minutes earlier before it rise because of the phenomena called atmospheric refraction. When sun rays reach the earth atmosphere they bent at different layers of atmosphere because each layer has different density so by bending the light rays enter the receiver eye two minutes earlier.