Stefan-Boltzmann law - Revision history

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	<onlyinclude>The '''Stefan-Boltzmann law''', also known as ''Stefan's Law'', is a law that expresses the ''total'' [[power]] per unit surface area (otherwise known as the ''intensity'') that is [[radiation\|radiated]] by an object, often taken to be a [[blackbody radiation\|blackbody]].</onlyinclude><ref>Marc L. Kutner. ''Astronomy: A Physical Perspective'', 2nd ed. New York, USA: Cambridge University Press, 2003.</ref> The formula used to determine at what wavelength the power peaks at is [[Wien's Law]]. The Stefan-Boltzmann Law explains how much power the [[Sun]] gives off given its [[temperature]] (or allows scientists to figure out how hot the sun is based on how much power strikes the Earth in a square [[metre]]). The law also predicts how much heat the Earth radiates into space. The Stefan-Boltzmann law doesn't say anything about the [[wavelength]] of light emitted, that is described by the [[Plank radiation formula]].		<onlyinclude>The '''Stefan-Boltzmann law''', also known as ''Stefan's Law'', is a law that expresses the ''total'' [[power]] per unit surface area (otherwise known as the ''intensity'') that is [[radiation\|radiated]] by an object, often taken to be a [[blackbody radiation\|blackbody]].</onlyinclude><ref>Marc L. Kutner. ''Astronomy: A Physical Perspective'', 2nd ed. New York, USA: Cambridge University Press, 2003.</ref> The formula used to determine at what wavelength the power peaks at is [[Wiens Law\|Wien's Law]]. The Stefan-Boltzmann Law explains how much power the [[Sun]] gives off given its [[temperature]] (or allows scientists to figure out how hot the sun is based on how much power strikes the Earth in a square [[metre]]). The law also predicts how much heat the Earth radiates into space. The Stefan-Boltzmann law doesn't say anything about the [[wavelength]] of light emitted, that is described by the [[Plank radiation formula]].

	This law is expressed as:		This law is expressed as:

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Jmdonev at 06:48, 27 August 2017

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	<onlyinclude>The '''Stefan-Boltzmann law''', also known as ''Stefan's Law'', is a law that expresses the ''total'' [[power]] per unit surface area (otherwise known as the ''intensity'') that is [[radiation\|radiated]] by an object, often taken to be a [[blackbody radiation\|blackbody]].</onlyinclude><ref>Marc L. Kutner. ''Astronomy: A Physical Perspective'', 2nd ed. New York, USA: Cambridge University Press, 2003.</ref> The formula used to determine at what wavelength the power peaks at is [[Wien's Law]]. The Stefan-Boltzmann Law explains how much power the [[Sun]] gives off given its [[temperature]] (or allows scientists to figure out how hot the sun is based on how much power strikes the Earth in a square [[metre]]). The law also predicts how much heat the Earth radiates into space. The Stefan-Boltzmann law doesn't say anything about the [[wavelength]] of light emitted, that is described by the [[Plank radiation formula]].		<onlyinclude>The '''Stefan-Boltzmann law''', also known as ''Stefan's Law'', is a law that expresses the ''total'' [[power]] per unit surface area (otherwise known as the ''intensity'') that is [[radiation\|radiated]] by an object, often taken to be a [[blackbody radiation\|blackbody]].</onlyinclude><ref>Marc L. Kutner. ''Astronomy: A Physical Perspective'', 2nd ed. New York, USA: Cambridge University Press, 2003.</ref> The formula used to determine at what wavelength the power peaks at is [[Wien's Law]]. The Stefan-Boltzmann Law explains how much power the [[Sun]] gives off given its [[temperature]] (or allows scientists to figure out how hot the sun is based on how much power strikes the Earth in a square [[metre]]). The law also predicts how much heat the Earth radiates into space. The Stefan-Boltzmann law doesn't say anything about the [[wavelength]] of light emitted, that is described by the [[Plank radiation formula]].

	This law is expressed as:		This law is expressed as:

	<center><m> \frac{P}{A} = e\sigma T^4 </m></center>		<center><math> \frac{P}{A} = e\sigma T^4 </math></center>

	where:		where:
	* <m>P</m> is the total power radiated (energy per unit time) per unit surface area		* <math>P</math> is the total power radiated (energy per unit time) per unit surface area
	* <m>A</m> is the surface area		* <math>A</math> is the surface area
	* <m>e</m> is the emissivity (how good of a radiator/absorber the object is). For most objects this is taken to be 1, although the Earth's [[atmosphere]] is an interesting [[deviations from blackbody radiation\|exception]].		* <math>e</math> is the emissivity (how good of a radiator/absorber the object is). For most objects this is taken to be 1, although the Earth's [[atmosphere]] is an interesting [[deviations from blackbody radiation\|exception]].
	* <m>\sigma</m> is the [[Stefan-Boltzmann constant]].		* <math>\sigma</math> is the [[Stefan-Boltzmann constant]].
	* <m>T</m> is the [[temperature]] of the object expressed in degrees [[Kelvin]]		* <math>T</math> is the [[temperature]] of the object expressed in degrees [[Kelvin]]

	The total radiated energy increases as temperature is increased. Based on a common observation wherein a heated object glows brighter as temperature increases, it should not be too surprising that objects radiate more energy with an increase in temperature.<ref>Kenneth Krane. ''Modern Physics'', 3rd ed. Hoboken, NJ, USA: John Wiley & Sons, 2012.</ref> As well, by manipulating the Stefan-Boltzmann equation, the [[temperature of the Earth without the greenhouse effect]] can be determined when values for power from the Sun and surface area of the Earth are used.<ref>R. Wolfson, (May 8, 2015). Energy, Environment and Climate, 2nd ed. New York, U.S.A.: Norton, 2012.</ref>		The total radiated energy increases as temperature is increased. Based on a common observation wherein a heated object glows brighter as temperature increases, it should not be too surprising that objects radiate more energy with an increase in temperature.<ref>Kenneth Krane. ''Modern Physics'', 3rd ed. Hoboken, NJ, USA: John Wiley & Sons, 2012.</ref> As well, by manipulating the Stefan-Boltzmann equation, the [[temperature of the Earth without the greenhouse effect]] can be determined when values for power from the Sun and surface area of the Earth are used.<ref>R. Wolfson, (May 8, 2015). Energy, Environment and Climate, 2nd ed. New York, U.S.A.: Norton, 2012.</ref>

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J.williams at 16:59, 12 August 2015

2015-08-12T16:59:07Z

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[[Category:Done 2015-04-01]]
<onlyinclude>The '''Stefan-Boltzmann law''', also known as ''Stefan's Law'', is a law that expresses the ''total'' [[power]] per unit surface area (otherwise known as the ''intensity'') that is [[radiation|radiated]] by an object, often taken to be a [[blackbody radiation|blackbody]].</onlyinclude><ref>Marc L. Kutner. ''Astronomy: A Physical Perspective'', 2nd ed. New York, USA: Cambridge University Press, 2003.</ref> The formula used to determine at what wavelength the power peaks at is [[Wien's Law]]. The Stefan-Boltzmann Law explains how much power the [[Sun]] gives off given its [[temperature]] (or allows scientists to figure out how hot the sun is based on how much power strikes the Earth in a square [[metre]]). The law also predicts how much heat the Earth radiates into space. The Stefan-Boltzmann law doesn't say anything about the [[wavelength]] of light emitted, that is described by the [[Plank radiation formula]].

This law is expressed as:

<center><m> \frac{P}{A} = e\sigma T^4 </m></center>

where:
* <m>P</m> is the total power radiated (energy per unit time) per unit surface area
* <m>A</m> is the surface area
* <m>e</m> is the emissivity (how good of a radiator/absorber the object is). For most objects this is taken to be 1, although the Earth's [[atmosphere]] is an interesting [[deviations from blackbody radiation|exception]].
* <m>\sigma</m> is the [[Stefan-Boltzmann constant]].
* <m>T</m> is the [[temperature]] of the object expressed in degrees [[Kelvin]]

The total radiated energy increases as temperature is increased. Based on a common observation wherein a heated object glows brighter as temperature increases, it should not be too surprising that objects radiate more energy with an increase in temperature.<ref>Kenneth Krane. ''Modern Physics'', 3rd ed. Hoboken, NJ, USA: John Wiley & Sons, 2012.</ref> As well, by manipulating the Stefan-Boltzmann equation, the [[temperature of the Earth without the greenhouse effect]] can be determined when values for power from the Sun and surface area of the Earth are used.<ref>R. Wolfson, (May 8, 2015). Energy, Environment and Climate, 2nd ed. New York, U.S.A.: Norton, 2012.</ref>

To read more about the physics of the Stefan-Boltzmann law please see [http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html#c1 hyperphysics].

==References==
{{reflist}}
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