A convex lens of power 5 D and a concave lens of power `7.5` D are placed in contact with each other
Channel: Doubtnut
Date: 2020-01-26

A convex lens of power 5 D and a concave lens of power `7.5` D are placed in contact with each other. What is the: a) power of this combination of lenses? b) focal length of this combination of lenses?