  We consider the velocity shift of light in presence of radiation emitted by a
black body. Within geometric optics formalism we calculate the bending angle of
a light ray when there is a gradient in the energy density. We model the
bending for two simplified cases. The bending angle is proportional to the
inverse square power of the impact parameter ($\propto 1/b^2$) when the
dilution of energy density is spherically symmetric. The bending angle is
inversely proportional to the impact parameter ($\propto 1/b$) when the energy
density dilutes cylindrically. Assuming that a neutron star is an isothermal
black body, we estimate the order of magnitude for such bending angle and
compare it with the bending angle by magnetic field.
