Why do we see a rainbow in the sky only after rainfall?
A. The water droplets behave like prism and reflects sunlight
B. The droplets behave like convex lens and disperses sunlight
C. The water droplets behave like prism and disperse sunlight
D. The water droplets behave like concave lens and disperses sunlight

Hint: Rainbow composed of 7 colors, and white light is composed of seven colors and the phenomenon of splitting of light into its constituent components is called dispersion of light. So, a rainbow is formed due to the dispersion of light in the skies but light is always there in the sky during the daytime.

Complete answer:
Light coming from the sun is composed of seven colors and we know when it passes through the prism it gets split into its constituents. So, after rainfall there is something present in the sky which acts like small prisms and they are the water droplets. These water droplets act like prisms and the scattering of light takes place.

So, the correct answer is “Option C”.

Note:
A rainbow is thus produced by the internal reflection and then dispersion of light takes place. The shape of the water droplets is spherical and we know that different colors have different wavelengths and they come out of the sphere at different angles which can be evidently proved from snell’s law. The white light now has been dispersed into its component colors, and the different colors travel in slightly different directions. You see red light coming from water droplets higher in the sky than violet light.