Question

convex lens of focal length 25 cm is placed at a distance x from a concave lens of focal length 7 cm. When a parallel beam is incident on the convex lens, it emerges as a parallel beam out of the concave lens, then the value of x is

Answer 1

Answer:

The value of X= 18cm

1/f = 1/f1 + 1/f2 − d/f1*f2

(f=∞)

x=18.