Optical scalars and the spherical gravitational lens

The optical scalar equations of Sachs are used to consider the gravitational lens effect of a static, spherically symmetric mass distribution. Two approaches are used, the first of which is an exact treatment of the bending approach used by Liebes and others, but without the restrictions imposed by the limited applicability of Einstein bending formula. The second approach emphasizes the close relationship between the optical parameters and the physical parameters associated with the mass distribution. This is useful in astrophysical applications, since a realistic case can often be treated by making small perturbations from some simple case. (author)