Why does rainbow forms and why the sunset is red; are some questions that can be simply explained to children, but somehow, the underlying answer can be so much interesting.
Professor Walter Lewin in this lecture [link] talks about all these.
But this is not the matter I would like to talk about.
I was fortunate to board a plane that flew during the hours of sunset. The experience was amazing.
|Scattering of light|
The picture above shows the phenomenon of light scattering. Light which comes from the sun is white. And whenever it hit a particle, the light will scatter. The chances of scattering are dependent on the wave length. Blue light has the highest chance. Therefore, this is reason we have blue sky.
The section in the middle of the picture has white-reddish color. This is because, the sun is very low in the horizon, and because the amount of air is massive, all the blue lights have been scattered off. Thus, we have red sunset.