Question

If a concave mirror of focal lenght ƒ₁ is placed at a distance of d from a convex lens of focal length ƒ₂. A light ray coming from infinity is falling on this combinatin and returns to infinity. The distance d must equal

(a)  – ƒ₁ + ƒ₂ 

(b) ƒ₁ + ƒ₂

(c) –2ƒ₁ + ƒ₂ 

(d) 2ƒ₁ + ƒ₂

Answer 1

Correct Option (d) 2ƒ₁ + ƒ₂

Explanation :

The arrangement and ray diagram is shown in figure

:.   d = 2f₁ + f₂