What causes cherenkov radiation?

by blokeice
Tags: cherenkov, light
blokeice is offline
Apr12-12, 12:09 PM
P: 2
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?
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AdrianTheRock is offline
Apr12-12, 01:02 PM
P: 136
Have you looked at http://en.wikipedia.org/wiki/%C4%8Cerenkov_radiation?
Bob S
Bob S is offline
Apr12-12, 05:24 PM
P: 4,664
The best derivation of Cerenkov radiation by a fast charged particle I have seen is the semi-classical derivation in Schilff Quantum Mechanics (2nd Edition) pages 267-271. Schiff derives the classical E and H fields, and the resulting Poynting vector P = E X H. He then gets the number of quanta radiated per unit path length in frequency interval ω to ω+dω:
[tex] dN=\frac{1}{137}\left(1-\frac{c^2}{n^2v^2} \right)\frac{d\omega}{c} \text{ photons per unit length}[/tex] which becomes for infinite index of refraction
[tex] dN=\frac{1}{137}\frac{d\omega}{c} \text{ photons per unit length}[/tex]
So the total number of quanta depends on wnat interval the frequency interval dω covers. Normally, the index of refraction is n ≤1 for wavelengths less than ~ 1000 Angstroms (UV).

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