Question

Rainbow appears due to dispersion of sunlight by __________.
(A) Water droplets
(B) Prism
(C) Glass Block
(D) All

Answer 1

Hint To find the correct answer, you firstly need to know that rainbow is a naturally occurring phenomenon and why and how it is produced. Also, as the name suggests, rainbow has a close correlation with the rain as rainbow is produced after the rain has stopped and there is still moisture in the air.

Complete step by step answer
As mentioned in the hint section of the solution, to solve the question, you first need to have a basic understanding about the rainbow. Let us share some information about rainbow first:
Rainbows are formed by a combination of refraction and reflection. You may have noticed that you see a rainbow only when you look away from the sun. It is so as the light from the sun enters a drop of water and is reflected from the back of the drop, as shown in the image. This is the only time when reflection happens in the whole process. As for refraction of the sunlight, the light rays from the sun are refracted both as they enter and as they leave the drop. Since the index of refraction of water varies with wavelength, the light is dispersed, and a rainbow is observed. Keep in mind that there is no dispersion caused by reflection at the back surface, since the law of reflection does not depend on wavelength. The actual rainbow of colors seen by an observer depends on the myriad of rays being refracted and reflected toward the observer’s eyes from numerous drops of water.


As we have described about the rainbow, it must be clear that the rainbow appears due to the dispersion of sunlight by water droplets that are present in the air due to the rain.

Hence, the correct option is option (A).

Note It should be noted that even though the VIBGYOR effect of white light or sun rays can be observed in a lab through the help of a prism, it would not be considered a rainbow since rainbow is a naturally occurring phenomenon and only the one due to the dispersion of light rays from water droplets is referred to as the rainbow.