If a concave and convex lens of equal focus are kept in contact what is the effective focal length?

1 Answer
Feb 12, 2016

Effective focal length in #oo#.

Explanation:

When two lenses are kept in contact, powers of the lenses are simply added.

Power of a lens is positive for convex lens and negative for concave lens.

Numerically power of a lens is given by #100/f# were #f# is focal length in centimeters.

As numerically, focal length is same but opposite in size, combined power will be #Zero# i.e. focal length is #oo# i.e. it is just equivalent to plane glass,