Refraction of Light

When light traveling in a medium (such as air) enters another medium (such as water), it generally bends at the surface separating the two media. But once it is in the second medium, it moves along a straight line. This phenomenon of bending of light at the surface separating two media is commonly known as refraction of light.

The Change in the path of light ray as it passes from one medium to another medium is called refraction of light. If the refracted ray bends towards the normal we say that the Medium 2 is denser than Medium 1.But if the refracted ray bends away from the normal we say that the Medium 2 is rarer than Medium 1. The light ray that falls normally i.e. at right angles from medium 1 to medium 2 then it does not bend or change its path. Such a ray goes undeviated in medium 2.

The surface separating the two media is also called the interface between them. Not the entire light incident on the interface between two media passes into the second medium after refraction; a small part of light gets reflected too.

Cause of Refraction:

Refraction of light takes place due to the change in the speed of light as it enters the medium 2 from medium 1.

As the density of different mediums is different so the speed of light changes as it goes from one medium to another.The change in direction depends on the amount by which its speed changes.

The speed of light reduces as it enters the denser medium so it bends towards the normal. and the speed of light increases as it enters the rarer medium so it bends away from the normal.

Effects of Refraction in Our Day to Day life:

1. A spoon dipped in water. The part of the spoon in air and water appears to be disjoint.

2. While standing in a clear pool of water, the bottom looks raised and our legs appear shorter.

3. The bottom of a glass tumbler filled with water appears raised when viewed from above.

4. If we put pins or coins in a tumbler filled with water and look from the side, their images appear enlarged.

5. Our ability to see also depends on refraction. Our eyes contain several transparent liquids. When light from an object enters our eyes, it is refracted at the surfaces of these liquids to produce an image.

6. Refraction is also responsible for such wonderful things as the twinkling of stars and the sparkling of diamonds.

Illustration: If while standing on the bank of a stream you wished to catch a fish swimming in the water in front of you, would you aim above, below or directly at the observed fish to catch it?

Solution: As the fish is inside the water, so the rays coming are refracted at the surface of water. The fish will appear to be at a higher position. In order to catch the fish we will aim below the position observed.

Sample Questions

(More Questions for each concept available in Login)

Question : 1

A rainbow is formed due to _____________ of sunlight by water droplets.
A. Refraction	B. Reflection	C. Dispersion	D. Scattering
Right Option : A
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Question : 2

Which of the following is used for splitting sunlight into seven colors?
A. Convex lens	B. Concave lens	C. Glass prism	D. Concave mirror
Right Option : C
View Explanation

Question : 3

When white light is passed through prism, it splits into ______________-
A. Eight colour	B. Nine colours	C. Seven colours	D. Five colours
Right Option : C
View Explanation