Radiometry

Information about Radiometry

In optics, radiometry is the field that studies the measurement of electromagnetic radiation, including visible light. Note that light is also measured using the techniques of photometry, which deal with brightness as perceived by the human eye, rather than absolute power.

Radiometry is important in astronomy, especially radio astronomy, and is important for Earth remote sensing. The measurement techniques categorized as radiometry in optics are called photometry in some astronomical applications, contrary to the optics usage of the term.

SI radiometry units
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Quantity	Symbol	SI unit	Abbr.	Notes
Radiant energy	Q	joule	J	energy
Radiant flux	F	watt	W	radiant energy per unit time, also called radiant power
Radiant intensity	I	watt per steradian	Wsr⁻¹	power per unit solid angle
Radiance	L	watt per steradian per square metre	Wsr⁻¹m⁻²	power per unit solid angle per unit projected source area. Sometimes confusingly called "intensity".
Irradiance	E	watt per square metre	Wm⁻²	power incident on a surface. Sometimes confusingly called "intensity".
Radiant exitance / Radiant emittance	M	watt per square metre	Wm⁻²	power emitted from a surface.
Radiosity	J or J_λ	watt per square metre	Wm⁻²	emitted plus reflected power leaving a surface
Spectral radiance	L_λ or L_ν	watt per steradian per metre³ or watt per steradian per square metre per hertz	Wsr⁻¹m⁻³ or Wsr⁻¹m⁻²Hz⁻¹	commonly measured in Wsr⁻¹m⁻²nm⁻¹
Spectral irradiance	E_λ or E_ν	watt per metre³ or watt per square metre per hertz	Wm⁻³ or Wm⁻²Hz⁻¹	commonly measured in Wm⁻²nm⁻¹

External links

Radiometry and photometry FAQ Professor Jim Palmer's Radiometry FAQ page (University of Arizona).

Optics (ὀπτική appearance or look in Ancient Greek) is a branch of physics that describes the behavior and properties of light and the interaction of light with matter.
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Measurement is the estimation of the magnitude of some attribute of an object, such as its length or weight, relative to a unit of measuremnt. Measurement usually involves using a measuring instrument, such as a ruler or scale, which is calibrated to compare the object to some
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Electromagnetic (EM) radiation is a self-propagating wave in space with electric and magnetic components. These components oscillate at right angles to each other and to the direction of propagation, and are in phase with each other.
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visible spectrum (or sometimes optical spectrum) is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light.
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Astronomy is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation).
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Radio astronomy is a subfield of astronomy that studies celestial objects in the radio frequency portion of the electromagnetic spectrum. Radio astronomy techniques are similar to optical techniques but radio telescopes have to be much larger due to the longer wavelengths being
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Earth remote sensing is data collection on the environment, geology, climate, and other characteristics of the Earth by means of sensors positioned in the air or in Earth orbit. Sensors used for this type of data gathering include those covering all parts of the electromagnetic spectrum.
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For the usage of this term in other areas of science, see .

Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical object's electromagnetic radiation.
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Si, si, or SI may refer to (all SI unless otherwise stated):

In language:

One of two Italian words:
sÃ¬ (accented) for "yes"
si

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Radiant energy is the energy of electromagnetic waves.^[1] The quantity of radiant energy may be calculated by integrating radiant flux (or power) with respect to time and, like all forms of energy, its SI unit is the joule.
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The joule (IPA: [dʒuːl] or [dʒaʊl]) (symbol: J) is the SI unit of energy.
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energy (from the Greek ενεργός, energos, "active, working")^[1] is a scalar physical quantity that is a property of objects and systems of objects which is conserved by nature.
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In radiometry, radiant flux or radiant power is the measure of the total power of electromagnetic radiation (including visible light). The power may be the total emitted from a source, or the total landing on a particular surface.
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City of license Cadillac, Michigan
Broadcast area [1]
Branding NewsTalk 1240
First air date 1945
Frequency 1240 kHz
Format News-Talk-Sports
Power 1,000 watts
Class C
Owner MacDonald Garber Broadcasting
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In radiometry, radiant intensity is a measure of the intensity of electromagnetic radiation. It is defined as power per unit solid angle. The SI unit of radiant intensity is watts per steradian (WÂ·sr^-1).
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The steradian (symbol: sr) is the SI unit of solid angle. It is used to describe two-dimensional angular spans in three-dimensional space, analogous to the way in which the radian describes angles in a plane.
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Radiance and spectral radiance are radiometric measures that describe the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle in a specified direction.
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square metre (also spelled meter, see spelling differences) is the SI derived unit of area, with symbol mÂ². It is defined as the area of a square whose sides measure exactly one metre.
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Irradiance, radiant emittance, and radiant exitance are radiometry terms for the power of electromagnetic radiation at a surface, per unit area. "Irradiance" is used when the electromagnetic radiation is incident on the surface.
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In physics, intensity is a measure of the time-averaged energy flux. To find the intensity, take the energy density (that is, the energy per unit volume) and multiply it by the velocity at which the energy is moving. The resulting vector has the units of power divided by area (i.e.
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Radiosity is the total of emitted and reflected radiation leaving a surface, in the fields of Optics and Heat Transfer. Hemispherical radiosity is the integral of the spectral intensity of reflected plus emitted radiation over the hemispherical solid angle^[1].
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1 metre =
SI units
1000 mm 0 cm
US customary / Imperial units
0 ft 0 in

The metre or meter^[1](symbol: m) is the fundamental unit of length in the International System of Units (SI).
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hertz (symbol: Hz) is the SI unit of frequency. Its base unit is cycle/s or s^-1 (also called inverse seconds, reciprocal seconds). In English, hertz is used as both singular and plural.
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In optics and heat transfer, reflectivity is the fraction of incident radiation reflected by a surface. In full generality it must be treated as a directional property that is a function of the reflected direction, the incident direction, and the incident wavelength.
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Radiometry

Information about Radiometry

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