Q24 of 223 Page 173

A boy with a mouth 5 cm wide stands 2 m away from a plane mirror. Where is his image and how wide is the image of his mouth ?

Height of mouth = 5cm

Mouth mirror distance = 2m


Second law of reflection says, angle of incidence is equal to the angle of reflection.


Thus, the image will form 2 m behind the mirror and the width of the image of boy's mouth will be 5 cm.


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22

What is the difference between regular reflection of light and diffuse reflection of light? What type of reflection of light takes place from?

(a) A cinema screen


(b) A plane mirror


(c) A cardboard


(d) Still water surface of a lake

 23

What can you see in a completely dark room? If you switch on an electric bulb in this dark room as a light source, explain how you could now see:

(a) The electric bulb


(B) a piece of white paper.

 24

The boy walks towards the mirror at a speed of 1m/s. At what speed does his image approach him?

 25

An extended object in the form of an arrow pointing upwards has been placed in front of a plane mirror Draw a labeled ray-diagram to show the formation of its image.