How is light measured?

Question

What scientific term is used to describe light intensity and what device measures it?

Answer 1

Put simply, intensity has units of power/area (for example, watt/meter^2). Most devices, like a photometer or photodetector, will measure the energy of the incoming light and figure out the intensity by averaging over time and dividing by the size of the optical sensor.

As a side note, the lux does not quite have units of pure intensity. The lux is a value based upon the luminosity function which "weights" different wavelengths according to how well the human eye sees them.

Answer 2

In a recent study, Boyce et al. (2001) suggest that light trespass be measured in a relative manner, at property boundaries, to take into account both light coming into the property as well as light inside the property. When designing the lighting for a site, imagine a vertical plane at the boundary between the site property and an adjacent property. Measure the illuminance on the vertical plane at the property boundary, directed toward the lighting design site, 180° away from the adjacent property. Then rotate 180° away from the lighting design site, and measure the illuminance on the vertical plane, directed toward the adjacent property. Calculate the ratio of the illuminance on the plane pointing toward the lighting design site to the illuminance on the plane pointing toward the adjacent property. If the ratio of the measured illuminances is less than unity (one), this implies that the design site receives more light from the adjacent property than the design site delivers to the adjacent property. If the ratio is greater than unity, then the design site delivers more light to the adjacent property than the adjacent property delivers to the site. The larger the ratio, the more likely light trespass complaints are to occur.

Answer 3

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Answer 4

The lux is the unit of light intesity and it is measured by a luxmeter.

Answer 5

Measurement of light

Main article: photometry

The following quantities and units are used to measure the quantity or "brightness" of light.

[edit]
SI photometry units Quantity Symbol SI unit Abbr. Notes
Luminous energy Qv lumen second lm·s units are sometimes called Talbots
Luminous flux F lumen (= cd·sr) lm also called luminous power
Luminous intensity Iv candela (= lm/sr) cd an SI base unit
Luminance Lv candela per square metre cd/m2 units are sometimes called nits
Illuminance Ev lux (= lm/m2) lx Used for light incident on a surface
Luminous emittance Mv lux (= lm/m2) lx Used for light emitted from a surface
Luminous efficacy lumen per watt lm/W ratio of luminous flux to radiant flux; maximum possible is 683.002


[edit]
SI radiometry units Quantity Symbol SI unit Abbr. Notes
Radiant energy Q joule J energy
Radiant flux Φ watt W radiant energy per unit time, also called radiant power
Radiant intensity I watt per steradian W·sr−1 power per unit solid angle
Radiance L watt per steradian per square metre W·sr−1·m−2 power per unit solid angle per unit projected source area.

Sometimes confusingly called "intensity".
Irradiance E watt per square metre W·m−2 power incident on a surface.

Sometimes confusingly called "intensity".
Radiant exitance / Radiant emittance M watt per square metre W·m−2 power emitted from a surface.

Sometimes confusingly called "intensity".
Spectral radiance Lλ
or
Lν watt per steradian per metre3 or

watt per steradian per square metre per hertz
W·sr−1·m−3
or

W·sr−1·m−2·Hz−1
commonly measured in W·sr−1·m−2·nm−1
Spectral irradiance Eλ
or
Eν watt per metre3 or
watt per square metre per hertz W·m−3
or
W·m−2·Hz−1 commonly measured in W·m−2·nm−1

Answer 6

first of all microw is completely wrong
watts are power

light is measured in from what i know 2 units

candlepower
and lumens

Answer 7

With the help of PHOTOMETER

Answer 8

- watts