Question

why colour of sun at sunrise and sunset appears red

Answer 1

During sunrise and sunset, the rays have to travel a larger part of the atmosphere because they are very close to the horizon. Therefore, light other than red is mostly scattered away. Most of the red light, which is the least scattered, enters our eyes. Hence, the sun and the sky appear red.

Answer 2

when white light of the sun enters to our atmosphere. it get scattered due to various particles of atmospher,and get scattered and the less wavelength colour appear ..that is red..