  Using the Fermat's principle in curved space-time with stationary type
metric, we have obtained the speed of light as a function of spatial
coordinates and hence the corresponding refractive index. The whole region with
space dependent gravity is divided into a number of overlapping transparent
refracting media with varying refractive index. The refractive index is found
to be increasing with the strength of gravitational field. Hence using the laws
of refraction, we have explained the gravitational bending of light. Further
using the conventional idea of total internal reflection of light while going
from denser to rarer medium, in the present scenario it is the propagation of
light from the region of ultra-strong gravitational field to relatively weaker
gravitational field region, we have proposed an alternative approach for no
emission of any kind of electromagnetic radiation from the surface of a
classical Schwarzschild Black Hole. We have further noticed that for an
observer in a uniformly accelerated frame, analogous to the Unruh radiation,
there can be emission of electromagnetic waves from the event horizon of a
classical black hole. This may be named as "black hole Unruh effect".
