CBSE Class 10 Science 2017 · Paper 31/2/3 · Question 17

The molecules of air and other fine particles in the atmosphere scatter light of shorter wavelengths (blue, violet) much more than light of longer wavelengths (red). At sunrise the sun is near the horizon, so its light passes through a much thicker layer of air — a much longer distance in the atmosphere — before reaching our eyes. Along this path most of the blue light and other shorter wavelengths are scattered away, and the light that reaches us is mainly of longer wavelengths, so the sun appears reddish. At noon the sun is overhead and its light travels a much shorter distance through the atmosphere. Only a little of the blue and violet is scattered away, so the sun appears white.