  We systematically explore the effect of the treatment of line opacity on
supernova light curves. We find that it is important to consider line opacity
for both scattering and absorption (i.e. thermalisation which mimics the effect
of fluorescence.) We explore the impact of degree of thermalisation on three
major types of supernovae: Type Ia, Type II-peculiar, and Type II-plateau. For
that we use radiative transfer code STELLA and analyse broad-band light curves
in the context of simulations done with the spectral synthesis code ARTIS and
in the context a few examples of observed supernovae of each type. We found
that the plausible range for the ratio between absorption and scattering in the
radiation hydrodynamics code STELLA is (0.8-1):(0.2-0), i.e. the recommended
thermalisation parameter is 0.9.
