A beam of light converges at a point P. Now a lens is placed in the path of the convergent beam 12cm form P. At what point does the beam converge if the lens is a) convex lens of focal length 20 cm, and b) a convex lens of focal length 16cm?

Explanation

`(1)/(v)-(1)/(12)=(1)/(-16)`
`v=48 cm`