A rainbow has a circular shape because?
A. The earth is spherical
B. The raindrops are spherical
C. The sun is spherical
D. None of these

Hint: Rainbow is always formed after a rainfall as the sun rays fall on the raindrops. It takes the form of a multicoloured circular arc.

Complete step by step solution:
A. The earth is spherical:
The shape of the rainbow is not dependent on the spherical shape of the earth, it is totally dependent on the angle at which the sun light meets the raindrops so the shape of earth does not cause the rainbow to be curved in shape. So this answer is wrong.

B. The raindrops are spherical:
In order to understand this point, let’s see how rainbows are formed:
rainbows are formed when the sunlight is refracted by the raindrops in the atmosphere when the rays of sunlight falls on the water droplets it enters the water droplet then the light rays are refracted to the backside of the droplet as the sunlight comes out of the water droplet it is refracted once again and a rainbow is formed , here sunlight is white in color and the water droplets acts as a prism which refracts the white light and makes it scatter in different colors. Then the question arises why the rainbow is spherical in shape, the answer to this is , the raindrops are spherical in shape and because of this shape the raindrop can scatter the sunlight in incident in all directions but only the droplets that reflects the light in
45 degrees forms a rainbow so this is the correct answer.

C. The sun is spherical in shape:
There is no effect of the sun being spherical in shape on a rainbow as whatsoever shape the sun has it will still have a white light which is scattered by the raindrops in the atmosphere, so this is the wrong answer.

D. None of these

The answer to this question is that the raindrops are spherical in shape.

Note: The curved shape of the rainbow depends on what angle the raindrops refract the sunlight. It should be exact \[{{45}^{\circ }}\] for a rainbow to be formed.