36. A body is located on a wall. Its image of equal size is to be obtained on a parallel wall with the help of a convex lens. The lens is placed at a distance ’ d ’ ahead of second wall, then the required focal length will be ?

36. A body is located on a wall. Its image of equal size is to be obtained on a parallel wall with the help of a convex lens. The lens is placed at a distance ’ d ’ ahead of second wall, then the required focal length will be ?

(a) only \( \frac{d}{4} \)

(b) only \( \frac{d}{2} \)

(c) more than \( \frac{d}{4} \) but less than \( \frac{d}{2} \)

(d) less than \( \frac{d}{4} \)

Answer :  (b) only \( \frac{d}{2} \)