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,