Thin lenses — Describe

What effect do thin converging and thin diverging lenses have on a parallel beam of light?

A thin converging (convex) lens refracts a parallel beam of light so that all the rays meet at a single point on the far side, called the principal focus. A thin diverging (concave) lens refracts a parallel beam so that the rays spread out (diverge) as though they came from a principal focus on the same side as the incoming light.