# 17-21-043

photon number

number of photons

Np

quotient of radiant energy and photon energy

where Qe is radiant energy, h is the Planck constant, and is the frequency of the corresponding electromagnetic wave

Note 1 to entry: Photon number can also be expressed by the time integral of the photon flux, Φp, over a given duration, Δt:
.

Note 2 to entry: The photon number has unit one.

Note 3 to entry: This entry was numbered 845-01-29 in IEC 60050-845:1987.

Note 4 to entry: This entry was numbered 17-930 and 17-829 in CIE S 017:2011.

Publication date: 2020-12