What is Luminous intensity: Definition and 14 Discussions

In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The SI unit of luminous intensity is the candela (cd), an SI base unit.
Photometry deals with the measurement of visible light as perceived by human eyes. The human eye can only see light in the visible spectrum and has different sensitivities to light of different wavelengths within the spectrum. When adapted for bright conditions (photopic vision), the eye is most sensitive to greenish-yellow light at 555 nm. Light with the same radiant intensity at other wavelengths has a lower luminous intensity. The curve which measures the response of the human eye to light is a defined standard, known as the luminosity function. This curve, denoted V(λ) or






y
¯


(
λ
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{\displaystyle \textstyle {\overline {y}}(\lambda )}
, is based on an average of widely differing experimental data from scientists using different measurement techniques. For instance, the measured responses of the eye to violet light varied by a factor of ten.

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  1. A

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  2. flying_bear

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  3. Paulpaulpa

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  4. G

    Mirror box with 1 candela of luminous intensity light source

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  5. Barnak

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  6. A

    Luminous intensity: from Volt to Candela/m2

    Homework Statement I use a probe for converting optical power to an electrical current. I need to convert Volt to candela/m2. The sensor, a photodiode, measure the brightness of the monitor leaning the probe on the glass (so there is no distance between the monitor and the sensor). The sensor...
  7. finnch

    UVA vs UVB: Why does UVA penetrate deeper into the skin?

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  8. finnch

    UVA/UVB Light: Why does UVA penetrate deeper into the skin?

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  9. 2

    Stefan-Boltzmann law, luminosity, brightness and magnitude?

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  10. L

    Unit solid angle and finite angle

    Homework Statement A point source emits visible light isotropically. Its luminous flux is 0.11 lumen. Find the flux whithin the cone that has half angle of 30 degree from the light source. Homework Equations luminous flux = luminous intensity * solid anlge The Attempt at a Solution I tried...
  11. S

    Should luminous intensity be a fundamental unit?

    It seems to me that luminous intensity should really be put in terms of energy, not a special unit (which itself is based on some arbitrary specification of energy.) The other 5 units and Avogadro's number should be the only fundamental units.
  12. Amith2006

    Luminous intensity due to an isotropic point source of light

    Does the luminous intensity due to an isotropic point source of light at a point on a surface depend on the angle it makes with the normal to the surface?
  13. Amith2006

    Luminous intensity in different directions

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  14. B

    SI unit for luminous intensity

    This is the SI unit for luminous intensity. The definition relates to blackbody radiation emitted at a certain temperature for a certain material (so I guess it ISN'T blackbody!), platinum, I think. Except... I don't understand the necessity for the introduction of this unit. Isn't...
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