  In order to explain light curve (LC) for Supernova (SN) we derive a classical
formula for the conversion of the flux of kinetic energy into radiation. We
then introduce a correction for the absorption adopting an optical depth as
function of the time. The developed framework allows to fit the LC of type Ia
SN 2005cf ( B and V ) and type IIp SN 2004A (B,V,I and R ). A relativistic
formula for the flux of kinetic energy is also derived in terms of a Taylor
expansion and the application is done to the LC of GRB 050814. The decay of the
radioactive isotopes as a driver the LC for SNs is also reviewed and a new
formulation is introduced. The Arnett's formula for bolometric luminosity is
corrected for the optical depth and applied to SN 2001ay.
