  We explore the possibility that a single relativistic shock, where the gas
dynamics is coupled with radiation, can fit the light curves of long GRBs. For
this we numerically solve the one dimensional relativistic radiation
hydrodynamics equations with a single initial shock. We calculate light curves
due to the evolution of this shock in terms of the velocity of the shock, the
opacity of the gas, mass density and density of radiated energy. We explore how
the variation of each of these parameters provides different features in the
light curves. As examples we include the fitting of two long GRBs.
