The problem of propagation of electromagnetic waves in a gravitational field can be reduced to the problem of wave propagation in a material medium in flat space-time. This method is used here to calculate the scattering cross section of a Schwarzschild black hole and the polarization of the scattered wave. It is shown that the polarization of the wave (as measured at infinity) is not affected by the presence of the spherically symmetric gravitational field of the black hole. The light scattered from a rotating or "live" black hole is, however, expected to be polarized for an incident unpolarized plane wave. This may offer a new way to detect a live black hole.

• Received 27 September 1972

DOI:https://doi.org/10.1103/PhysRevD.7.2807