  We compute the scattering cross section of Reissner-Nordstr\"om black holes
for the case of an incident electromagnetic wave. We describe how scattering is
affected by both the conversion of electromagnetic to gravitational radiation,
and the parity-dependence of phase shifts induced by the black hole charge. The
latter effect creates a helicity-reversed scattering amplitude that is non-zero
in the backward direction. We show that from the character of the
electromagnetic wave scattered in the backward direction it is possible, in
principle, to infer if a static black hole is charged.

General Relativity and Quantum Cosmology