  The radial motion along null geodesics in static charged black hole
space-times, in particular, the Reissner-Nordstr\"om and stringy charged black
holes are studied. We analyzed the properties of the effective potential. The
circular photon orbits in these space-times are investigated. We found that the
radius of circular photon orbits in both charged black holes are different and
differ from that given in Schwarzschild space-time. We studied the physical
effects of the gravitational field between two test particles in stringy
charged black hole and compared the results with that given in Schwarzschild
and Reissner-Nordstr\"om black holes.
