When white light passes through a prism or raindrops, it undergoes a phenomenon called dispersion, which causes it to split into a spectrum of colors. This occurs due to the different wavelengths of light bending at different angles as they pass through a medium.
White light is composed of a combination of all the visible colors in the electromagnetic spectrum, including red, orange, yellow, green, blue, indigo, and violet. Each of these colors corresponds to a different wavelength, with red having the longest wavelength and violet having the shortest.
As white light enters a prism or raindrop, it slows down and bends (refracts) as it transitions from one medium to another. However, different colors of light have different wavelengths, which results in them bending at slightly different angles as they pass through the medium. This phenomenon is known as refraction.
The refraction of light inside the prism or raindrop causes the different colors to separate. The shorter wavelengths (blue and violet) are refracted more than the longer wavelengths (red and orange). As a result, the light gets spread out into a fan-like shape, creating a spectrum of colors.
In the case of a prism, the separated colors emerge on the other side of the prism and form a rainbow-like spectrum. Each color appears at a specific angle and position in the spectrum, with red being the least refracted and appearing on the outer edge of the spectrum, while violet appears on the inner edge.
When it comes to raindrops, the process is similar. Sunlight enters the raindrop, undergoes refraction and internal reflection, and then exits the raindrop. The different colors of light are separated inside the raindrop and form a circular rainbow, with red on the outer edge and violet on the inner edge.
In both cases, the phenomenon of dispersion allows us to see the various colors that make up white light, creating the beautiful spectrums we observe.