Question

Rainbow is produced by the dispersion of sunlight by tiny raindrops in the air.
A: True
B: false

Answer 1

Rainbow is visible when the white light of the sun splits into its seven composite colours. A raindrop in the atmosphere would act similar to that of a prism. There would be a refraction, internal reflection and another refraction. Refractive index is dependent on wavelength.

Complete answer:
Let us have an understanding of what is meant by refraction and reflection before approaching the problem.
Reflection can be considered as the change in the direction of a light ray at the interface of two physical media with different refractive indices such that the light ray is bounced back into the initial media. A basic example of reflection can be spotted at the reflection of light by metallic surfaces.
Refraction on the other hand can be explained as the change in direction of a light ray as it passes from one medium to another. An example is the change in direction of light ray as it passes from air to water.
As we have discussed, a raindrop in the atmosphere would act similar to that of a prism.
In the tiny drops of water in the air, light enters the droplet and undergoes internal reflection inside the droplet, on the other side of the drop, and after the reflection the light beam is split into different components on the basis of its wavelength.
The sunlight is composed of light from the entire visible spectrum. And the refractive index of a medium depends on the wavelength of light. As white light contains light beams of different wavelengths on being reflected back, they split into their components, this process is called dispersion. And when emerging out of the droplet the light would appear in different colours rather than a single white beam. This process when happening on a massive scale in the atmosphere causes rain.

Hence the correct answer is true.

Note:
The reason for dispersion of light is the wavelength to refractive index relationship. There is a corresponding change in velocity due to this change. Though the velocity of light is a constant in a medium, it varies from media to media.