There hardly is anyone who does not take the time to stop and look at the sky when the rainbow appears. This natural phenomenon truly is magnificent, but it is quite rare, which makes it even more spectacular and precious.
Scientifically speaking, a rainbow appears as a result of reflection, refraction and dispersion of light in the droplets of water, which causes the spectrum of light to appear in the form of colorful arc. A number of events need to occur before rainbow is formed, which is why we see it so rarely. First, there has to be a certain level of moisture in the air and sky, and this usually requires a rainy day or a period right after the summer rainstorm. Second, the position of the sun also matters, and it must take a low angle, approximately 42 degrees relative to the observer and behind him. Then, the part of the sky where the sun is has to be completely clear of any obstructions to the light such as clouds, and the rest of the sky needs to have rain or moist in order for the rainbow to appear. When all these elements are combined, we are likely to see the magnificent colorful arc in the sky.
In addition to the rainbow which occurs as a result of the fortunate combination of sun, clouds and rain, there are some other types of rainbow as well. These can also provide the viewers with interesting effect, and some of them are even rarer than the rainbows we see after the storm
Double rainbow – it may have happened that you saw this phenomenon up in the sky as well. It happens when the light is reflected in the water droplets two times instead of only one. When this happens, a secondary rainbow is formed above the primary one. It is longer, but less intense, and its colors are reversed.
Moonbow (lunar rainbow) – this type of rainbow is very rarely seen, but it can appear very spectacular. It is formed on the night of the full moon when it is raining. Moonbow differs from ordinary rainbow because it looks pale or even white, since the moonlight is not bright enough to form a colorful rainbow.
Supernumerary rainbows – this phenomenon is also called stacker rainbows, and it occurs when the light is reflected in the droplets of similar sizes. It is reflected only once, but it goes along several different paths within one droplet. This results in the appearance of several faint rainbows inside of the primary and outside of the secondary one, and it is a rather rare phenomenon.
Cloud rainbow – a rainbow of different shape and much broader than the usual rainbow can occur in the sky when there are thin clouds, and usually above large water surfaces. It occurs when the light is reflected through very tiny water droplets in the clouds, and not through the droplets that form rain.
Red rainbow – red or monochromatic rainbow, as the name says, consists of only one color – red. It occurs right after rainfall during dusk or dawn, and it happens because green and blue – the colors of the spectrum with shorter wavelength – are scattered by air and dust. The remaining light consists of the colors with longer wavelengths, such as yellow and red, and this is when red rainbow is formed.