Transition radiation produced in dihedral and trihedral angles

Method of electrical images is applied to the description of transition radiation generated when a charges particle passes through a dihedral angle formed by perfectly conducting planes. It is shown that the electromagnetic field generated when a charged particle passes through a dihedral angle α = π/m is equivalent to the field generated by 2m charged particles which instantaneously start to move. Transition radiation in trihedral angle is also considered.