Cherenkov radiation: threshold β > 1/n, opening angle cos θ_C = 1/(β·n)

Cherenkov's 1934 radiation: a charged particle traversing a transparent dielectric medium with phase velocity c/n emits a coherent shockwave of photons at the Cherenkov angle cos θ_C = 1/(β·n), provided β > 1/n (threshold). Frank-Tamm…