Dispersion of light is the phenomenon in which white light, which appears colorless to the human eye, is separated into its component colors when it passes through a medium, such as a prism or a droplet of water. This separation occurs because different colors of light have different wavelengths, and they bend or refract at different angles as they pass through the medium. As a result, the light disperses, revealing its constituent colors.

The key factor behind the dispersion of light is the property of refraction. Refraction refers to the bending of light as it passes from one medium to another with a different optical density, such as from air to water or from air to a prism. When a beam of white light enters a medium at an angle, the different colors that make up the white light have varying speeds and wavelengths. This causes each color to refract or bend by a different amount as it transitions into the medium.

The amount of bending, or refraction, that occurs depends on the index of refraction of the medium. The index of refraction is a measure of how much a particular medium slows down light compared to its speed in a vacuum. Different colors of light have different wavelengths, with shorter wavelengths corresponding to colors like violet and blue, and longer wavelengths corresponding to colors like yellow and red.

When white light enters a medium, such as a prism, the shorter wavelengths (violet and blue) are refracted more than the longer wavelengths (yellow and red). As a result, the different colors are spread out or dispersed, forming a spectrum of colors. This spectrum is commonly referred to as a rainbow, with violet appearing at one end and red at the other. The other colors of the spectrum, such as blue, green, yellow, and orange, appear in between.

The phenomenon of dispersion of light is also responsible for various natural phenomena, such as the formation of rainbows, the colors seen in soap bubbles, and the splitting of light by a diamond or a gemstone. It is also an essential principle behind the functioning of devices like prisms, spectrometers, and optical fibers.

In summary, dispersion of light occurs due to the variation in the refractive indices of different colors of light as they pass through a medium. This causes the different colors to bend or refract by different amounts, resulting in the separation and spreading out of the component colors of white light.