Q18 of 223 Page 198

An object 3 cm high is placed at a distance of 10 cm in front of a converging mirror of focal length 20 cm.

Find the position, nature and size of the image formed.

U = 10 cm

F = 20 cm


Height of object = 3 cm


Such that using the mirror formula, we get


v = +20 cm;


The image formed is behind the converging mirror; Virtual and erect ; 6 cm high


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16

A converging mirror forms a real image of height 4 cm of an object of height 2 cm placed 20 cm away from the mirror:

(i) Calculate the image distance.


(ii) What is the focal length of the mirror?

 17

An object of size 9.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed so that a sharp focused image can be obtained? Find the size and nature of image.

[Hint. Find the value of image distance (v) first. The screen should be placed from the mirror at a distance equal to image distance].

 19

A concave mirror has a focal length of 4 cm and an object 2 cm tall is placed 9 cm away from it. Find the nature, position and size of the image formed.

 20

When an object is placed 20 cm from a concave mirror, a real image magnified four times is formed. Find:

(a) the focal length of the mirror.


(b) Where must the object be placed to give a virtual image three times the height of the object?