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IEVref:845-21-045ID:
Language:enStatus: Standard
Term: luminous intensity
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Symbol: Iv
I
Definition: density of luminous flux with respect to solid angle in a specified direction

Iv=dΦvdΩ

where Φv is the luminous flux emitted in a specified direction, and Ω is the solid angle containing that direction

Note 1 to entry: For practical realization of the quantity, the source is approximated by a point source.

Note 2 to entry: The distribution of the luminous intensities as a function of the direction of emission, e.g. given by the polar angles (ϑ, φ), is used to determine the luminous flux, Φv, within a certain solid angle, Ω, of a source:

Φv=ΩIv(ϑ,φ)sinϑ dφ dϑ.

Note 3 to entry: Luminous intensity can be derived from the spectral radiant intensity distribution by

Iv= Km0Ie,λ(λ)V(λ)dλ

where Km is maximum luminous efficacy, Ie,λ(λ) is the spectral radiant intensity at wavelength λ, and V(λ) is spectral luminous efficiency.

Note 4 to entry: The corresponding radiometric quantity is "radiant intensity". The corresponding quantity for photons is "photon intensity".

Note 5 to entry: The luminous intensity is expressed in candela (cd = lm·sr−1).

Note 6 to entry: This entry was numbered 845-01-31 in IEC 60050-845:1987.


Publication date:2020-12
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