# What causes cherenkov radiation?

1. Apr 12, 2012

### blokeice

If you get an electron going faster than the local speed of light i know that it starts emitting light, but why does it do this?, furthermore, In a theoretical material with an infinite index of defraction (a.k.a light is stopped within it), wouldn't that cause the system to quickly go to near absolute zero?

2. Apr 12, 2012

$$dN=\frac{1}{137}\left(1-\frac{c^2}{n^2v^2} \right)\frac{d\omega}{c} \text{ photons per unit length}$$ which becomes for infinite index of refraction
$$dN=\frac{1}{137}\frac{d\omega}{c} \text{ photons per unit length}$$