Bounding the greybody factors for the Reissner-Nordstrom black holes

A black hole can emit radiation called Hawking radiation. Such radiation seen by an observer outside the black hole differs from the original radiation near the horizon of the black hole by the so-called "greybody factor". In this paper, the bounds of the greybody factors for the Reissner-Nordstrom black holes are obtained. These bounds can be derived by using the 2 x 2 transfer matrices. It is found that the charges of black holes act as good barriers.