Which phenomenon is associated with black holes due to quantum effects near the event horizon?

• A. Cerenkov radiation
• B. Hawking radiation
• C. Bremsstrahlung
• D. Synchrotron radiation

Answer: (B)

Quantum effects near the event horizon produce Hawking radiation. In quantum field theory, vacuum fluctuations can create particle-antiparticle pairs; near the horizon, one member of a pair can fall into the black hole while the other escapes, so an outside observer sees radiation emanating from the black hole. This radiation has a thermal spectrum and a temperature that is inversely proportional to the black hole’s mass, meaning smaller black holes radiate more and can eventually evaporate. The other names listed correspond to radiation produced by different physical processes—Cerenkov radiation requires a medium and a particle moving faster than light in that medium, Bremsstrahlung arises from decelerating charges, and synchrotron radiation comes from charged particles spiraling in magnetic fields—none of which are the quantum-horizon effect described here.