Question

A plano-convex lens of focal length 30 cm has its plane surface silvered. An object is placed 40 cm from the lens on the convex side. The distance of the image from the lens is(a) 18 cm(b) 24 cm(c) 30 cm(d) 40 cm

Answer 1

the correct answer is option is (b).

Answer 2

Answer:

B) 24cm

Explanation:

Focal length = 30cm ( Given)

Distance of object = 40cm ( Given)

Therefore, object -

1/v-1/u = 1/f

1/v = 1/30-1/40

1/v = 4-3/120

1/v = 1/120

Thus, v = 120cm The image will act as object for the lens.

u = 120 cm and f = 30 cm

1/v-1/u = 1/f

1/v = 1/30+1/120

v = 24

Thus, the distance of the image from the lens is 24cm