How is a rainbow an example of light dispersion?

A rainbow is an example of light dispersion as it separates white sunlight into its constituent colours.

When sunlight encounters a raindrop, it undergoes a process called dispersion. This is the phenomenon where light is split into its various component colours. The white light from the sun contains all the colours of the spectrum, but when it hits the raindrop, it is refracted, or bent, and this bending varies depending on the wavelength of the light.

The shorter wavelengths (like blue and violet) are bent more than the longer ones (like red and orange). This is why the colours in a rainbow are always in the same order, with red on the outside and violet on the inside. After this refraction, the light is reflected off the inside surface of the raindrop and refracted again as it exits the drop. This second refraction further separates the colours, creating the spread of colours we see in a rainbow.

It's important to note that each raindrop only produces one colour, but because there are so many raindrops in a shower, we see the full spectrum of colours. The exact colour we see from a particular drop depends on the angle between the sun, the drop, and our eyes. This is why rainbows always appear in the part of the sky opposite the sun and why they are curved. The angle needed for the light to exit the drop and reach our eyes is the same all along that curve.

In summary, a rainbow is a beautiful and fascinating example of light dispersion. It demonstrates how white light is composed of different colours, each with its own unique wavelength, and how these can be separated by refraction and reflection within a raindrop.