Qualitative features of the transition radiation from slow particles vs fast ones

Transition radiation arises while the charged particle crosses the interface between two media with different electromagnetic properties, e.g. the boubdary between vacuum and the conductor in the simplest case. The interest to the transition radiation is due to its yield rapidly increases with the particle's enegy rise. Since that, the main accent in researches and practical use is paid to the radiation from the high enegy particles. This forms among the researches the specific intuitive picture concerning the radiation peculiarities, which could be not valid in the general case. The present article systematically studies the characteristics (both the spectral-angular density and the polarization) of the transition radiation under oblique incidence of the particle on the conducting plane. The genesis of differences of that characteristics in the case of slow (slightly relativistic and non-relativistic) particles from the intuitively expectable ones for the ultrarelativistic particles is clearly traced out.