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SAI INTERNATIONAL SCHOOL
Class8
Lesson notes
Subject-Physics
CH- Light
Subtopic- Characteristics of image & Multiple Reflection

Some features of image formed by a plane mirror:

 Image is always formed behind the mirror.
 It is a virtual image, which means it cannot be obtained on screen.
 Image is upright and laterally inverted.
 Image size and distance are equal to object size and distance.

Uses:
 Dressing mirror
 Kaleidoscope
 Periscope

Multiple Images: When two or more mirrors are placed at some angles to each
other, we get to see multiple images. Let us take an example in which two mirrors

are placed opposite to each other. If an object is placed between them, its image is
formed in both the mirrors. The image in one mirror would act as an object for
another mirror and this sequence would continue. This will result in the formation of

multiple images.

The number of images formed depends on the angle between the two mirrors. This
can be calculated by using the following formula:

Number of Images = (360/Angle) – 1

So,

1. If the given mirrors are at a right angle to each other, 3 images will be formed.

n = (360/90) -1 = 4-1 = 3

2. If the given mirrors are at 30° angle, we shall get 11 images.

n = (360/30)- 1 = 12 -1 = 11

3. When the mirrors are kept opposite and parallel to each other, there would be
infinite number of images formed.

n = (360/0) - 1 = infinite