A concave lens is placed in contact with a convex lens of focal length `25 cm`. The
Channel: Doubtnut
Date: 2020-08-02

A concave lens is placed in contact with a convex lens of focal length `25 cm`. The combination produces a real image at a distance of `80 cm`, when an object is at a distance of `40 cm`. What is the focal length of concave lens ?