What happens when a light ray strikes a mirror?

When a ray of light strikes a mirror,it is reflected in a different direction

A Ray of Light reflected from the Mirror - Teachoo.png

What is Incident Ray and Reflected Ray?

The light ray which strikes a surface is called Incident Ray

The light ray which comes back from surface after reflection is called Reflected Ray



What is Normal 

It is a line which is perpendicular to mirror at point of incidence

 

How to Draw Normal

Let Mirror be denoted by AB

Let Point where incident ray strikes mirror be O

We draw a line ON which is perpendicular to mirror AB at point O

This ON is called Normal Ray

Incident, Reflected and Normal Rays in the Mirror - Teachoo.png

 

What is the Angle of Incidence and Reflection?

 

Angle between Normal and Incident Ray is called Angle of Incidence

Let it be denoted by i

 

Angle between Normal and Reflected Ray is called Angle of Reflection

Let it be denoted by r

 

Note that 

Angle of Incidence is always equal to the Angle of Reflection

In our case, 

Angle i = Angle r

Incident, Reflected and Normal Rays in the Mirror - Teachoo - 2.jpg

Laws of Reflection

 

There are 2 laws of Reflection

  1. The Incident ray, Reflected ray and the Normal, all lie in the same plane
  2. The Angle of Incidence is always equal to Angle of Reflection

 

So, in our figure above,

Incident ray OP, reflected ray OQ and Normal ray ON all lie on the same plane

And,

Angle of incidence = Angle of Reflection



Check the figure below

Law of Reflection - Experiment Image - Teachoo.png

In this figure, the incident ray, reflected ray and normal all lie on the table. So, they all lie on the same plane.

And, Angle of Incidence = Angle of Reflection.

Check out the video below for the full experiment

  1. Class 8
  2. Chapter 16 Class 8 - Light

About the Author

Davneet Singh's photo - Teacher, Computer Engineer, Marketer
Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.