Concepts

Class 10
Chapter 10 Class 10 - Light - Reflection and Refraction

We saw that in Reflection of light,

light bounces off the surface

But sometimes, light does not bounce off the surface

Light goes inside a different medium

This going inside different medium is called refraction

Now, suppose we have Light coming from air into Water

The Light doesn't reflect from water... it goes inside water

And light travels slower in water than air,

So, it changes direction

This changing of direction is called Refraction

Let's define it formally

## What is Refraction of Light

The change in direction of light

when it passes from one medium to another

obliquely

is called Refraction of light

Note: - We write obliquely here because light should come at an angle, it should not be perpendicular to the surface

### Example 1

Suppose we put a pencil in a glass of water

It appears to be displaced (at the place air and water meet)

This is because of refraction of light

(Light bends when it moves from air to water)

### Example 2

Suppose we write something on a piece of paper

We put a glass slab over it

The letter appears to be raised

This is also because of refraction of light

## What Causes Refraction of Light?

It is caused by change in Speed of Light in Different Mediums

Explanation

Speed of Light is different in different mediums

Example-Speed of Light is more in Air than in Glass

When light travels from one medium to another (like from air to glass), there is difference in speed of light in 2 mediums

This causes Refraction of light

## Questions

Question 1 Page 176 - A ray of light travelling in air enters obliquely into water. Does the light ray bends towards the normal or away from the normal? Why?

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#### Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo