Question

Why the rainbow appears in the atmosphere at specific air humidity?

I would like to get a detailed description for better understanding, some schemes, examples based on basic relations. I would like to get some additional articles, books, or sources to read more too.

Answer 1

Rainbows need both moisture and sunshine, so you won't see a rainbow unless the sun is out. A rainbow is an excellent demonstration of the dispersion of light, and proof that visible light is made up of a spectrum of wavelengths, each associated with a distinct colour.Water is denser than air, so when sunlight passes through the air to a raindrop it slows and changes direction (or bends). Physicists call this process refraction. Each individual droplet of water acts as a tiny prism that both disperses the light and reflects it back to your eye.

When sunlight is refracted by the droplet of moisture, the observer - standing with the sun behind them - will see an array of colours in an arc as the refracted sunlight is reflected back.You may be surprised to hear that double rainbows are actually quite common - they occur because the sunlight is reflected twice inside the raindrop. This also means the sequence of the colours is reversed, so look closely next time you see one.