The number of photons per unit time and per unit area in the wavelength band 400 to 700 nm. Units: micromoles per second per square meter (μmol•s-1•m-2).
Note: There are 6.0222 x 1023 photons (Avogadro’s number) in one mole of photons.
NOTE: This definition was changed in RP-16-17 Addendum 4.
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