How does Cherenkov radiation work?
The Cherenkov effect is a beautiful example of how symmetry and constraints in a medium produce observable phenomena. When a charged particle travels through a dielectric medium at a speed exceeding the phase velocity of light in that medium, it creates a coherent shock wave of electromagnetic radiation—analogous to a sonic boom. The radiation is emitted at a characteristic angle θ given by cos θ = 1/(βn), where β is the particle's speed relative to light in vacuum and n is the refractive index. This is not a quantum effect per se; it follows directly from classical electrodynamics of anisotropic media, as I derived with Frank. But we must ask: what does experiment say? The blue glow in reactor pools is a direct confirmation. This principle now enables detection of high-energy particles in neutrino telescopes and cosmic-ray experiments.
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