|
||||||||||||||||||
The Vavilov-Cerenkov Effect and the Doppler Effect in the Motion of Sources with Superluminal Velocity in VacuumIt is customary to consider only ``subluminal'' light sources, or sources moving with a velocity lower than the velocity of light in vacuum . It is assumed in this connection that the Vavilov--Cerenkov effect and the anomalous Doppler effect are possible only in media and waves for which the refractive index . For this reason, the phase velocity of the waves is . Yet, as is well known, there exist also ``superluminal'' sources, with velocity . Examples are light spots produced on a remote screen by a rotating source of light or particles. The spot velocity is , where is the angular velocity of source rotation and is the distance to the screen. The condition can be realized on the Earth, and is practically always realized under astronomical conditions for pulsar radiation. It is emphasized in the article that superluminal sources are equivalent in a wide range to subluminal ones, and, concretely, can generate Cerenkov radiation in vacuum and in a medium with $n(\omega)
|
||||||||||||||||||
|