Question

.A converging and diverging lens of equal focal lengths are placed coaxially in contact. Find the focal length and power of the combination? 2

Answer 1

For a combination effective focal length

1/f = 1/f1+1/f2

here 1/f1= -1/f2

therfore 1/f=0

and f=infinite

ie Power P = 1/f =0