  We investigate the thermal photon production-rates using one dimensional
boost-invariant second order relativistic hydrodynamics to find proper time
evolution of the energy density and the temperature. The effect of
bulk-viscosity and non-ideal equation of state are taken into account in a
manner consistent with recent lattice QCD estimates. It is shown that the
\textit{non-ideal} gas equation of state i.e $\epsilon-3 P \neq 0$ behaviour of
the expanding plasma, which is important near the phase-transition point, can
significantly slow down the hydrodynamic expansion and thereby increase the
photon production-rates. Inclusion of the bulk viscosity may also have similar
effect on the hydrodynamic evolution. However the effect of bulk viscosity is
shown to be significantly lower than the \textit{non-ideal} gas equation of
state. We also analyze the interesting phenomenon of bulk viscosity induced
cavitation making the hydrodynamical description invalid. It is shown that
ignoring the cavitiation phenomenon can lead to a very significant over
estimation of the photon flux. It is argued that this feature could be relevant
in studying signature of cavitation in relativistic heavy ion collisions.
