EN
Transition radiation emitted when a nonrelativistic particle (β=0.2-0.5) enters a surface irregularity shaped as a rectangular step and a rectangular groove and having the dielectric constant ε=1.4-3.8 has been investigated. The angular distribution of the radiation intensity as well as its dependence on the height of the irregularities, the width of the groove and the distance between the irregularity edge and the entry point of the particle have been calculated on the basis of the theory of Bagiyan and Ter-Mikaelyan.