| quotient of the integrated value of the radiant flux of all wavelengths emitted by fluorescence (fluorescence band) and the radiant excitation power irradiating the fluorescent material for a given excitation wavelength Note 1 to entry: The fluorescent radiant efficiency is a measure of the external radiant efficiency of the fluorescent material; the internal radiant efficiency is obtained by taking a quotient of the emitted radiation and the radiant excitation power that is absorbed by the fluorescent material. Note 2 to entry: In this definition, the excitation wavelength is considered to be monochromatic. However, in practice, the excitation radiation will have a wavelength range and distribution. Note 3 to entry: Fluorescence is understood to include both fluorescent and phosphorescent phenomena with time constants short enough to be ignored for the application. Note 4 to entry: The fluorescent radiant efficiency has unit one.
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