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The luminous flux accounts for the sensitivity of the eye by weighting the power at each wavelength with the luminosity function, which represents the eye's response to different wavelengths. The luminous flux is a weighted sum of the power at all wavelengths in the visible band. Light outside the visible band does not contribute.
Luminous flux incident on a surface Luminous exitance, luminous emittance M v: lumen per square metre lm/m 2: L −2 ⋅J: Luminous flux emitted from a surface Luminous exposure: H v: lux second: lx⋅s L −2 ⋅T⋅J: Time-integrated illuminance Luminous energy density ω v: lumen second per cubic metre lm⋅s/m 3: L −3 ⋅T⋅J: Luminous ...
The luminosity of a radio source is measured in W Hz −1, to avoid having to specify a bandwidth over which it is measured. The observed strength, or flux density, of a radio source is measured in Jansky where 1 Jy = 10 −26 W m −2 Hz −1. For example, consider a 10 W transmitter at a distance of 1 million metres, radiating over a ...
The Schechter luminosity function [5] provides an approximation of the abundance of galaxies in a luminosity interval [+]. The luminosity function has units of a number density n {\displaystyle n} per unit luminosity and is given by a power law with an exponential cut-off at high luminosity
By contrast, luminous flux is weighted according to a model (a "luminosity function") of the human eye's sensitivity to various wavelengths; this weighting is standardized by the CIE and ISO. [2] The lumen is defined as equivalent to one candela-steradian (symbol cd·sr): 1 lm = 1 cd·sr.
Flux density: E e [nb 5] watt per square metre W/m 2: M⋅T −3: Radiant flux received by a surface per unit area. This is sometimes also confusingly called "intensity". Spectral irradiance Spectral flux density: E e,ν [nb 6] watt per square metre per hertz W⋅m −2 ⋅Hz −1: M⋅T −2: Irradiance of a surface per unit frequency or ...
The Stefan–Boltzmann law may be expressed as a formula for radiance as a function of ... that the energy flux density from the Sun is 29 ... The luminosity of ...
The CIE 1924 photopic V(λ) luminosity function, [cie 3] which is included in the CIE 1931 color-matching functions as the y (λ) function, has long been acknowledged to underestimate the contribution of the blue end of the spectrum to perceived luminance. There have been numerous attempts to improve the standard function, to make it more ...