Question

An object of height 1.2m is placed before a concave mirror of focal length 20 cm so that

a real image is formed at a distance of 60cm from it. Find the position of an object.

What will be the height of the image formed? ​

Answer 1

Explanation:

from mirror formula,

1/f = 1/u + 1/v

1/-20 = 1/u +1/-60

1/u = 1/-60+1/20= 2/60

thus, u = 60/2 or 30cm

object distance is 30cmcm at the left of mirror

now, height of object is 1.2m = 120 cm

height of image is given by h'

-v/u = h'/h

-60/30 = h'/120

h' = - (2* 120) = -240 cm

or the height of image is 2.4 m