THE CONVEX MIRROR

A convex mirror reflects light rays in such a way that the effect is similar to that of a concave lens. Incident rays, when parallel, are spread out (Fig. 1a) after they are reflected from the surface. Converging incident rays, if the angle of convergence is just right, are collimated by a convex mirror (see Fig. 1b). When you look at the reflection of a scene in a convex

Fig. 1. (a) A convex mirror spreads parallel incident light rays. (b) The same mirror collimates converging incident light rays.

mirror, the objects all appear reduced. The field of vision is enlarged, a fact that is used to advantage in some automotive rear-view mirrors.
The extent to which a convex mirror spreads light rays depends on the radius of curvature. The smaller the radius of curvature, the greater is the extent to which parallel incident rays diverge after reflection.