Question

A spherical convex surface separates object and image space of refractive index 1.0 and 4/3. If radius of curvature of the surface is 10 cm. find its power .

Answer 1

Let us see where does the parallel rays converge (or diverge) on the principal axis. Let us call it the focus and the corresponding length the focal length f. Using

with proper values and signs, we have

Since, the rays are converging, its power should be positive. Hence,