Question

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

v = -60
f = - 20
height of image = 1.2
Then,
1/f = 1/v + 1/u
-1/20 = -1/60+1/u
-1/20+1/60 = 1/u
-60+20/20×60 = 1/u
-40/1200 = 1/u
-1/30 = 1/u
so,
u = -30
Now,
height of image / height of object = -v/u
height of image/height of object = -(-60)/-30
height of image/ 1.2= -60/30
height of image/1.2= -2
height of image = -2×1.2
height of image = -2.4 cm