Jul 17, 2019
What is the Cherenkov Effect?
The Cherenkov effect is the characteristic blue glow of an underwater nuclear reactor. It is caused by an electromagnetic radiation, emitted when a beta particle (or charged particle) passes through a dielectric medium (not air) at a speed greater than the velocity of light in that medium. The index of refraction for that medium (n) must be greater than 1 in order for the effect to occur. The Cherenkov effect does not occur in air because the index of refraction of air is too similar to that of a vaccum.
So, in short, the blue glow seen when a nuclear reactor, submerged in water, reaches criticality is from the movement of charged particles (at a speed faster than the speed of light in water) within the water.
