Question

What is the geometrical shape of the wave front when a plane wave passes through convex lens?

Answer 1

Dear Student,

When a plane wavefront passes through a convex lens, it is turned into a contracting wave front of radius f and therefore receives a positive curvature +1/f.
The radius of curvature (R) of a surface is taken as a positive number if it increases the curvature of the waves – i.e. converges the waves and negative if it decreases the curvature of the ways – i.e. diverges the waves.

A surface that converges a wavefront is taken a positive e.g. a convex lens.

Regards