How Does a Rainbow Form?

A rainbow is a colorful arc that appears in the sky when sunlight is refracted and reflected by water droplets in the air. The formation of a rainbow involves three steps: refraction, reflection, and dispersion.Refraction is the bending of light when it passes from one medium to another with a different density. When sunlight enters a water droplet, it is refracted at the surface of the droplet and changes its direction.Reflection is the bouncing of light when it hits a surface. When the refracted sunlight reaches the back of the droplet, it is reflected back to the front of the droplet.Dispersion is the splitting of white light into its component colors. When the reflected sunlight exits the droplet, it is refracted again at the surface of the droplet and changes its direction. However, this time, the angle of refraction depends on the wavelength of the light. Shorter wavelengths (such as violet and blue) are refracted more than longer wavelengths (such as red and orange). This causes the white light to split into a spectrum of colors.The colors of the rainbow are arranged in the order of decreasing wavelength and increasing refraction: red, orange, yellow, green, blue, indigo, and violet. This is the same order as the colors of the spectrum that are produced by a prism. To see a rainbow, the observer must be positioned between the sun and the water droplets, and the sun must be behind the observer. The angle between the sun, the observer, and the center of the rainbow is about 42 degrees.

The bending of light when it passes from one medium to another with a different density is called by......