Photon statistics

Photon statistics are the case of Bose-Einstein statistics with an unspecified total number of particles. The average number of particles in a state s is given by the Planck distribution:

<ns> = 1/(exp(Es/ kBT) - 1)

where Es is the energy of a particle in s, T is the temperature, and kB is Boltzmann's constant.

Black body radiation may be described through photon statistics: the continuous absorption and re-emission of photons by the walls of the body, which has nonzero volume and temperature.