Problem 5.26

By means of plotting find: (a) the path of a light ray after reflection from a concave and convex spherical mirrors (see Fig. $5.4,$ where $F$ is the focal point, $O O^{\prime}$ is the optical axis); (b) the positions of the mirror and its focal point in the cases illustrated in Fig. $5.5,$ where $P$ and $P^{\prime}$ are the conjugate points.