# e-ILV

The e-ILV provides free access to all the terms and definitions contained in the international standard CIE S 017:2020 ILV: International Lighting Vocabulary, 2nd edition.

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# 17-21-042

photon energy

Qp; Q

product of the Planck constant and frequency
Qp = hν
where h is the Planck constant and ν is the frequency of the corresponding electromagnetic wave

Note 1 to entry: Photon energy can be emitted, transferred or received.

Note 2 to entry: The energy of monochromatic radiation, QPF, by a photon flux of photons of frequency ν is equal to the photon number, Np, times the photon energy (QPF = Np·h·ν).

Note 3 to entry: The corresponding radiometric quantity is "radiant energy". The corresponding photometric quantity is "luminous energy".

Note 4 to entry: The photon energy is expressed in joule (J = W·s).

Publication date: 2020-12