(a) Can you measure rough focal length of a convex lens? If yes, why?
(b) Can you measure rough focal length of a concave lens ? If not, why not?

The focal length of a convex lens is

Can we find rough focal length of a convex mirror ? If yes, how? If no, why not?

Rahul find the rough focal length of a convex lens. He is trying same method to find the focal length of concave lens, will he be successful. Justify your answer with help of ray diagram.

Concave lens : Negative focal length :: convex lens …………..