  We discuss the transition radiation process $\nu \to \nu \gamma$ at an
interface of two media. The medium fulfills the dual purpose of inducing an
effective neutrino-photon vertex and of modifying the photon dispersion
relation. The transition radiation occurs when at least one of those quantities
have different values in different media. We present a result for the
probability of the transition radiation which is both accurate and analytic.
For $E_\nu =1$MeV neutrino crossing polyethylene-vacuum interface the
transition radiation probability is about $10^{-39}$ and the energy intensity
(deposition) is about $10^{-34}$eV. At the surface of the neutron stars the
transition radiation probability may be $\sim 10^{-20}$. Our result on three
orders of magnitude is larger than the results of previous calculations.}
