Concepts

Class 8
Chapter 16 Class 8 - Light

We know that plane mirror reflects light.

The reflected ray from one mirror can act as the incident ray on another mirror.

Hence, the ray of light can be reflected again.

Hence, a reflected light can be reflected again.

Just like in this image,

## Example 1 - Periscope

A periscope is a long, tubular device through which a person can see objects that are not in direct line of sight.

It is a device which is used

• to see over the heads of a crowd
• by soldiers sitting in a trench to observe enemy activities outside
• it is used by submarines to see ships over the surface of water in the sea.

In a periscope,

Two mirrors are placed parallel to each other

Image of one mirror is reflected to other mirror and we able to see image

### Example 2 - Barber Shop Mirrors

We are able to see the back of the head with the help of 2 mirrors

The light is reflected from our hair on the small mirror.

This light is automatically reflected to main mirror

So we are able to see the back of out head

## Multiple Reflection when 2 mirrors are placed side by side

If 2 mirrors are placed close to each other,it produces Multiple reflections

The number of Images formed depends on the angle between two images

It is given by a simple formula

Let’s also see the Formula working in reality

#### Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo