How can we explain the reddish appearance of sun at sunrise or sunset? Why does it not appear red at noon?

Explanation

The reddish appearance of the sun at sunrise or sunset is due to scattering of light by the molecules of air and other fine particles in the atmosphere have size smaller than the wavelength of visible light from the sun near the horizon. It passes through thicker layers of air and larger distance in the earth's atmosphere before reaching our eyes and most of the blue light and shorter wavelengths are scattered away by the particles.
So, only red light, being of higher wavelength reaches us which gives reddish appearance of sun at sunrise or sunset.

At noon, the sun appears white, not red, as only a little of the blue and violet colours are scattered as light from the Sun overhead would travel relatively shorter distance.