Why does light bend in a prism?

optical components

Firstly,I will explain what a prism is a prism with a triangular base is used mainly for observing of dispersion of white light.

This is an triangular prism with base angles 60°,60°,60°.

We can also get a prism with base angles 45°,45°,90°.

Like this

But a triangular prism with base angles 60°,60°,60° is used for observing dispersion of white light.

Now I’ll explain why light bends on passing through prism-

White light consists of a collection of component colours.When white light passes through the prism,it’s constituent colours separate from each other due to their difference in speed in glass bending by a different angle in respect to the incident ray

Let me explain using real life examples-

Imagine you and 2 of your friends are athletes and ate running holding hands but suddenly a lake approaches.Now you and your friends have to swim all the way through the lake to reach land again.One of your friends is an expert swimmer while the other is a rookie.You stand somewhere in the middle.Naturally it is difficult for the three of you to swim holding your hands instead you divide and reach the other side alone.

This phenomena in terms of light is known as dispersion of light i.e spilling of white light into it’s constituent colours.

Now,I’ll go I little onto depth and explain why light doesn’t disperse while travelling through a glass slab

Simply because both the reflecting surfaces are parallel to each other so all of the bending (and dispersion) that takes place at the first interfaces is exactly reversed at the second, ‘undoing’ the effect of the first interface

Thanks for reading.



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