Cerenkov effect
noun/tʃɛˈɹɛŋkəf ɛˈfɛkt/
Etymology Named after Pavel Alekseyevich Cherenkov.
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Natural sciences, Physical sciences, Physics The emission of light (Cerenkov radiation) that occurs when a charged particle passes through an insulator at a speed greater than the speed of light in that medium; the characteristic blue glow from a nuclear reactor.