text: A variant of FRET couples this effect to absorption in quantum dot nanoparticles for high-sensitivity biologicalimaging.
full_question: A variant of FRET couples this effect to absorption in quantum dot nanoparticles for high-sensitivity biologicalimaging. H.E.S.S., an array of telescopes in Namibia, uses this effect to detect gamma rays. A Heavisidefunction appears in the integral for the energy change per unit length from this phenomenon, which is proportionalto the charge squared. The cosine of the Mach cone angle produced by this effect equals one over theproduct of index of refraction and beta. Super-Kamiokande detects this effect from neutrinos colliding withelectrons in a tank of water. This phenomenon occurs if a charge particle is accelerated beyond the velocity oflight for a given medium. For 10 points, name this bluish glow seen near spent nuclear reactors. 
first_sentence: A variant of FRET couples this effect to absorption in quantum dot nanoparticles for high-sensitivity biologicalimaging.
raw_answer: Cherenkov radiation [or Vavilov-Cherenkov radiation]