In this dissertation, we have explored some concepts of the black holes physics, such as thermodynamics of black holes, Hawking radiation, and black holes' perturbations. Hawking radiation with Hawking-Bekenstein entropy of black holes are the most important problems in the black holes physics. It is believed that research in these fields will lead the physicists to the right theory of quantum gravity. There are different theories and methods that give the Hawking-Beckenstein entropy of black holes. Some of these approaches have been investigated, and based on the outcomes of Loop Quantum Gravity; the entropy is calculated in the grand canonical ensemble. The event horizon's temperature has been worked out by various methods. One of these ways is based on the space time's perturbations. In this method, the most important idea is that we consider the emitted fields and particles by black hole as the sources of perturbations. The wave equation controls the behavior of these perturbations. In a few space times the wave equation can be solved analytically. Then, we can extract dissimilar results, like Hawking temperature, grey body factor, absorption cross section of black hole, and quasi normal modes, by imposing suitable boundary conditions. Moreover, there are some methods that approximate the solutions in low energy fields and particles limit. However, to compute the Hawking temperature of event horizon, we have to see the fields and particles in high energy limit. Therefore, we are not likely to compute all of the black holes' temperatures using this method. One of our objections in this thesis was studying the behavior of Hawking temperature under conformal transformation. A group of these transformations alter the metric so that the wave equation can be solved analytically in these deformed space times, and this enables us to calculate the Hawking temperature. Making use of a purely geometrical approach, it has been proved that the surface gravity and Hawking temperature is invariant under conformal transformation in advance. The method that is presented in this thesis also gives the identical temperature for the original metrics and the transformed versions. Although, this approach is not as general as the geometrical method however it is a more quantum mechanical technique. Keyword: black holes, gravitational waves, Hawking radiation