Light produced by charged particles when they pass through an optically transparent medium at speeds greater than the speed of light in that medium.
For example, when electrons from a nuclear reactor travel through shielding water, they do so at a speed greater than that of light through water and they displace some electrons from the atoms in their path. This causes emission of electromagnetic radiation that appears as a weak bluish-white glow. The phenomenon is named for Pavel A. Cherenkov (19041990), who discovered it; he shared a 1958 Nobel Prize with Igor Y. Tamm (18951971) and Ilya M. Frank (19081990), who interpreted the effect.