a technique in which individual photons are counted using a single-photon detector.

Virtual photons are a fundamental concept in particle physics and quantum field theory that play a crucial role in describing the interactions between electrically charged particles.

Quantum of electromagnetic radiation energy.

Random fluctuations in light detection.

In physics, a photon gas is a gas-like collection of photons, which has many of the same properties of a conventional gas like hydrogen or neon – including pressure, temperature, and entropy.

(physics) A photon, whose energy is too small to be detected, that is one of a cloud associated with a charged particle.

(New Age) A mythical dangerous belt of photons emanating from the Pleiades that will collide with the Earth in the near future according to New Age mystics.

(of a black hole) A spherical limit around a black hole at such distance that any photon meeting it tangentially is constrained to travel in a circular orbit; (more loosely) the region between this limit and the event horizon.