Question

An object is placed at some distance from a convex mirror of focal length 20 cm such that a image is formed on a screen which is two times magnified. The distance through which the lens should be moved so that a real image is again formed at same screen which is two times diminished is

• A. 30 cm
• B. 20 cm
• C. 40 cm
• D. 60 cm

Answer 1

Answer: (A)

30 cm

Answer 2

m = – 2 or $- \frac { 1 } { 2 }$

u = – x

f = 20 cm

solving x₁ = 30 cm and x₂ = 60 cm

Dx = 30 cm