When it rains and at the same time the sun illuminates the sky, an arch formed by different colors called a rainbow usually appears, with which everyone who appreciates it is amazed, since it is a phenomenon of nature that can be very spectacular, or at least quite curious.
What is the rainbow
A rainbow appears in the sky thanks to the refraction and reflection of sunlight in the drops of water caused by the rain. As a summary, it could be said that it is a luminous band that presents different colors due to the decomposition of light . When we observe it, it is seen that it has an arc shape, hence its name, although it really has a circular shape, although it cannot be seen complete unless we are located in a very high area.
As you know, there are several conditions for a rainbow to form. Here we mention them while we explain the process of formation of the rainbow :
- When the sunlight illuminates the drops of water from the rain, which behave like small prisms if they are in the ideal position, the white light from the sun separates forming a set of rays of different colors that separate as the rays move within the water droplets.
- Later the rays hit the inner wall of the drop, and are reflected back, colliding with the surface of the drop to go outside.
- Each ray will have a different angle and color and as this effect occurs in millions of drops, it makes us see a rainbow .
As a summary, to say that for the formation of a rainbow it has to rain, there must be the presence of sunlight and that the sunlight passes through the drops at a certain angle. When a rainbow forms, the sun is always behind you.
Newton already stated that light , like the rainbow, is made up of seven colors. The 7 colors of the rainbow are:
Although they are not really only 7 colors, as it happens in the spectrum of visible light, that is, that light that we can distinguish, since the human eye only responds to wavelengths between 390 to 750 nm.
In the rainbow there is a continuous gradient of colors , so at least hundreds of different colors could be perceived . However, the aforementioned colors are the ones that best allow us to understand it, with violet being towards the inner end of the rainbow and red at the outer end.
The full rainbow
As mentioned in the previous section, the rainbow is really a circle . The most common is that when we observe it we see only an arc, this happens because we are located on the earth’s surface.
In order to see the complete rainbow or the complete circumference of the rainbow, in addition to having all the factors that make the formation of a rainbow possible: raindrops, sun and an ideal angle between both factors, we would have to rise above the earth’s surface, in addition to the rainbow being free of obstacles. This means that if, for example, we are located on top of a mountain, despite being elevated, the mountain can be an obstacle, since it prevents the sun’s rays from passing through and the shadow it gives prevents the rainbow from forming. full. However, if we are flying in an airplane or in a helicopter, we could appreciate this spectacular phenomenon, since the shadow that these means of transport project is very small if we compare it with the radius that forms a rainbow.
Surely you have ever looked at the sky and found not only one rainbow, but two. This second rainbow is called the double rainbow .
The double rainbow occurs less frequently, this phenomenon occurs when the sun’s rays pass through the lower part of the water drops , and reach our vision thanks to the rebound that occurs within the drop. The fact that there are two bounces of light causes the rays to cross and come out of the drop of water in the opposite direction. In this way, a double rainbow or also called a secondary rainbow is formed , which will be above the main rainbow. Its intensity is less than that of the primary rainbow, since the rays lose energy in the bounces, and the stripes, in addition to being wider, are in the opposite direction, that is, the red color is at the inner end and the violet color on the outside.