The gravitational lens effect of various black hole types

In this thesis, the gravitational lensing effect of different type of black holes and its dependence on various parameters has been investigated. Firstly, non-rotating black hole assumption is considered. Under this assumption, the motion of the photon and the dependence of its path bending on various parameters have been studied. Secondly, a rotating black hole has been assumed. For such a geometry, bending, lensing effect, and possible black hole shadows are investigated in details. The variation of lensing is also considered for the double black holes. Calculations are tested with the observed data. Lensing parameters of supermassive black holes at the center of galaxies are re-estimated. In addition, quasar observations that show similar lensing effects are also considered for comparison. Finally, recent observation results of the supermassive black hole at the center of the M87 galaxy are considered for new estimations. Key words: Gravitational lensing, black holes, mass in general relativity.