Question

40. If a magnification -1 is to be
obtained by using a converging lens
of focal length 12 cm, then the
object must be placed
(A) at 24 cm distance
(B) within 12 cm distance
(C) beyond 24 cm distance
(D) None of the above​

Answer 1

Answer:

(A) at 24 cm distance

Explanation:

Magnification = -1 = image size / object size

=> Image size = - object size

That means image is inverted and of equal size.

This happens when object is at 2F.

So, obj position = 2F = 2 × 12 = 24 cm