Why rainbow is not always visible?

The rainbow is an impressive atmospheric phenomenon, the nature of which has interested mankind at all times. Thus, the Persian astronomer Qutb al-Din ash-Shirazi, who lived in 1236-1311, was the first to give a fairly accurate explanation of the appearance of the rainbow. The partial physical picture of the rainbow was first described in the book “De radiis visus et lucis in vitris perspectivis et iride” written by Marc Anthony de Dominis back in 1611. A full explanation of the phenomenon (relevant to this day) was given by Rene Descartes in 1637.

Physics of the rainbow. A white ray of light passing through a drop of water (rain or fog) refracts and breaks into its constituent parts: red, orange, yellow, green, blue, blue and violet — the colors of the rainbow. The effect is caused by the fact that the rays of the different colors are refracted different. Red color deviates the least, violet is more. The most obvious example is the experience of Newton with the use of a glass prism. He made an important conclusion from it: white light is composite, it is a mixture of all the colors of the rainbow(spectrum).

Why rainbow is not always visible? This phenomenon is possible only when the sun comes out from the opposite side of the thundercloud, where it had just rained. Sometimes you can see the double rainbow, the second a little higher on the first (primary), it is much dimmer and the colors in it are reversed. This happens in cases when the beam of light reflected from the inner surface of a drop of water not once but two (due to this, the colors are in reverse order). The third rainbow in natural conditions is extremely rare.

It is quite simple to recreate this phenomenon at home: put a glass of water on the window on the sunny side or just spray water against sunlight - and you will be able to see all colors of the spectrum.