The rainbow is na optical phnomenon caused by refraction of the light in the raindrop and it arises due to the sepation of the colors that form the sunlight. The rainbor can be observed whenever there are droplets of water suspended in the atmosphere and the sunlight is reflecting above the observer at low altitude or angle.

That phenomenon can happen during or after a rain, and it occurs due to the dispersion of the light. In the rainbow, we can observe the following colors: red, orange, yellow, blue, indigo and violet – however, most people only see six colors.

• Dispersion and Refraction

Dispersion is the phenomenon that causes the separation of a wave in several spectral components, and refraction is na optical phenomenon that occurs when the light changes from a propagation medium to another, example, air and water.

As previously mentioned, the rainbow is caused by the dispersion of sunlight, that suffers refraction from the raindrops.

The sunlight is a white light wave composed of several colors, and when this light falls on a drop of water, the rays that penetrate it are retracted and suffers dispension. The color separation, that we can see with the naked eye, occurs due to a new refraction process, where the colored light beam, inside the water, is reflected on its internal surface.

• Optical illusion

In fact, the rainbow doesn’t exists, it is na optical illusion, whose position is always in the opposite direction of the in relation to the observer. It is important to emphasized that all raindrops refract and reflect the sunlight in the same way, but only the light of some of them arrives to the observer’s eyes.