  We study the effect of back-reaction on the evaporation of quantum black
holes. The method used is based on quantum tunneling formalism as proposed in
[4]. We give a more realistic picture by considering the fact that a black hole
looses its energy while modes are tunneled outside the event horizon. It is
shown how the tunneling quantum field modes affect the geometry and how this
change in geometry is arrested in the quantum field. Exploiting this we
calculate the modified (nonthermal) radiation spectrum, associating energy
fluxes and discuss various issues related with these. The results obtained here
are often expected on physical grounds, but, importantly we find them in a
quantitative manner.
