Question

an object is placed 40 centimeters from a convex lens of focal length 30 centimeters. if a concave lens of focal length 15 centimeter is introduced between the convex lens and the image formed such that it is 20-centimeter from the convex lens, find the change in the position of the image

Answer 1

Thats the one, I guess:)

Answer 2

hiiii I think i know u mudit

For the convex lens, f₁ = +30 cm and object distance u₁ = - 40 cm.

        1 / f₁ = 1/v₁ - 1/u₁

      => 1 / +30 = 1/v₁ - 1/-40

       => 1/v₁ = 1/30 - 1/40

       => 1/120

=> v₁ = +120 cm, a real image is formed

       On introducing a concave lens, f₂ = -50 cm

and u₂ = 120 - 20 = +100 cm from the concave lens

            1/f₂ = 1/v₂ - 1/u₂

       = 1/-50 = 1/v₂ - 1/+100

       = v₂ = - 100 cm

A virtual image is formed at all the distances of 100 cm from the concave lens.

The change in position between the real image and the virtual image is 100 cm + 100 cm = +200 cm to the left of its original position