Question

A concave mirror of focal length is placed at a distance of d from a convex lens of focal length .A beam of light coming from infinity and falling on this convex lens- concave mirror combination returns to infinity. The distance d must equal

• A. $\mathrm { f } _ { 1 } + \mathrm { f } _ { 2 }$
• B. $- \mathrm { f } _ { 1 } + \mathrm { f } _ { 2 }$
• C.
• D. $- 2 \mathrm { f } _ { 1 } + \mathrm { f } _ { 2 }$

Answer 1

Answer: (C)

Answer 2

:

$\therefore \mathrm { d } = 2 \mathrm { f } _ { 1 } + \mathrm { f } _ { 2 }$