There are 2 basic types of lenses: Convex and concave lens. A converging lens (Convex) takes light rays and bring them to a point. A diverging lens (concave) takes light rays and spreads them outward. In a convex lens, an incoming ray parallel to the principal axis is refracted through the principal focus. In a concave lens, an incoming ray parallel to the principal axis is refracted so that it appears to come from the principal focus.
Lenses – an Application of Refraction
