Question

A converging mirror forms a real image of height 4 cm of an object of height 1 centimetre placed 20 CM away from the mirror. Calculate the image distance. What is the focal length of the mirror?

Answer 1

Answer:

hi = 4cm

ho = 1cm

u=-20cm

(a) v=?

hi/ho=-v/u

where,

hi=height of the image

ho=height of the object

v=distance of the image from the mirror

u=distance of the object from the mirror

4/1=-v/-20

4 = v/20

v = 80cm

Let focal length of the mirror to be 'f'

1/f = 1/v + 1/u

1/f = 1/80 + 1/(-20)

1/f = 1/80 - 1/ 20

1/f = -5/80

f = -80/5 cm

f = -16 cm

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