Kirchhoff's law of thermal radiation

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	Black body - LearnThis.Info Enclyclopedia
		The deviations are determined by the both the geometrical structure and the chemical composition, and follow Kirchhoff's Law: emissivity equals absorptivity, so that an object that does not absorb all incident light will also emit less radiation than an ideal black body.
		The intensity of radiation from a black body at temperature T is given by Planck's Law of Radiation:
		The wavelength at which the radiation is strongest is given by Wien's law, and the overall power emitted per unit area is given by the Stefan-Boltzmann law.
	encyclopedia.learnthis.info /b/bl/black_body_1.html (514 words)

	Kirchhoff's law of thermal radiation - Wikipedia, the free encyclopedia
		Kirchhoff's law of thermal radiation, is a general statement equating emission and absorption in heated objects, proposed by Gustav Kirchhoff in 1859 (and proved in 1861), following from general considerations of thermodynamic equilibrium.
		Kirchhoff's Law has a corollary: the emissivity cannot exceed one (because the absorptivity cannot, by conservation of energy), so it is not possible to thermally radiate more energy than a black body, at equilibrium.
		At thermal equilibrium, the emissivity of a body (or surface) equals its absorptivity.
	en.wikipedia.org /wiki/Kirchhoff's_law_(thermodynamics) (392 words)

	Gustav Kirchhoff - Open Encyclopedia
		He coined the term "black body" radiation in 1862, and two sets of independent concepts in both circuit theory and thermal emission are named "Kirchhoff's laws" after him.
		He proposed his law of thermal radiation in 1859, and gave a proof in 1861.
		Kirchhoff formulated his current law voltage law for circuit analysis, which are now ubiquitous in electrical engineering, in 1845, while still a student.
	open-encyclopedia.com /Gustav_Kirchhoff (340 words)

	Kirchhoff's laws - Wikipedia, the free encyclopedia
		Kirchhoff's law (thermodynamics) is a theorem about thermal radiation from heated objects, equating emission and absorption, and is derived from general considerations of thermal equilibrium.
		Kirchhoff's circuit laws: This is a pair of rules (common in electrical engineering) to analyze electric circuits, which can be derived from Maxwell's equations.
		Kirchhoff's law(s), named after Gustav Robert Kirchhoff, is a term applied to two entirely different concepts.
	en.wikipedia.org /wiki/Kirchhoff's_laws (340 words)

	Kirchhoff's laws - Wikipedia, the free encyclopedia
		Kirchhoff's law (thermodynamics) is a theorem about thermal radiation from heated objects, equating emission and absorption, and is derived from general considerations of thermal equilibrium.
		Kirchhoff's circuit laws: This is a pair of rules (common in electrical engineering) to analyze electric circuits, which can be derived from Maxwell's equations.
		Kirchhoff's law(s), named after Gustav Robert Kirchhoff, is a term applied to two entirely different concepts.
	www.wikipedia.org /wiki/Kirchhoffs_laws (132 words)

	ASTR 1110 Lectures Spring 1999
		One of Kirchhoff's laws states that a hot opaque (optically thick) object emits a continuous thermal spectrum called a "blackbody" spectrum.
		The total amount of radiation emitted by a blackbody at all wavelengths is found by integrating the Planck function over all wavelengths.
		This is parameterized by the albedo, A, of the object, where A=0 is a perfectly black and absorbing surface, and A=1 is a perfectly reflective surface.
	lasp.colorado.edu /~colwell/astr3750-f00/dec5notes.html (620 words)

	Sketching the History of Statistical Mechanics and Thermodynamics
		Gustav Robert Kirchhoff (1824-1887) derives from the second law of thermodynamics that objects cannot be distinguished by their thermal radiation at a given uniform temperature, one must also use reflected light.
		Boltzmann formulates a statistical mechanical version of the second law of thermodynamics in the paper, "On the Relation Between the Second Law of the Mechanical Theory of Heat and the Probability Calculus with Respect to the Theorems on Thermal Equilibrium".
		Boltzmann suggests that one may derive the probabilistic picture from the kinetic one by heuristically assuming that all microstates must be realized in a system before returning to a specific microstate, and thus measured values should average the effects of such states.
	history.hyperjeff.net /statmech_slim.html (6746 words)

	Sketching the History of Statistical Mechanics and Thermodynamics
		Gustav Robert Kirchhoff (1824-1887) derives from the second law of thermodynamics that objects cannot be distinguished by their thermal radiation at a given uniform temperature, one must also use reflected light.
		Boltzmann formulates a statistical mechanical version of the second law of thermodynamics in the paper, "On the Relation Between the Second Law of the Mechanical Theory of Heat and the Probability Calculus with Respect to the Theorems on Thermal Equilibrium".
		Boltzmann suggests that one may derive the probabilistic picture from the kinetic one by heuristically assuming that all microstates must be realized in a system before returning to a specific microstate, and thus measured values should average the effects of such states.
	history.hyperjeff.net /statmech.html (6799 words)

	Sketching the History of Statistical Mechanics and Thermodynamics
		Gustav Robert Kirchhoff (1824-1887) derives from the second law of thermodynamics that objects cannot be distinguished by their thermal radiation at a given uniform temperature, one must also use reflected light.
		Planck's 1900 analysis did not, at the time, imply any new law about the microstructure of matter, nor was there any reason to believe that extrapolation of the Rayleigh-Jeans law signalled any failure of classical methods.
		James Clerk Maxwell (1831-79) reads a paper on kinetic theory, printed in 1860 as "Illustrations of the Dynamical Theory of Gases," using random velocity distributions for gases, and showing viscosity to be independent of temperature.
	history.hyperjeff.net /statmech.html (6799 words)

	CONK! Encyclopedia: Perpetual_motion
		Science: Conservation of energy, Thought experiment, Thermodynamic entropy, Second law of thermodynamics, Kirchhoff's law of thermal radiation
		People: George Westinghouse, Josef HoÃ«nÃ©-Wronski, Joseph Newman, John E.W. Keely
	www.conk.com /search/encyclopedia.cgi?q=Perpetual_motion (1516 words)

	Kirchhoff's law of thermal radiation - Wikipedia, the free encyclopedia
		Kirchhoff's Law has a corollary: the emissivity cannot exceed one (because the absorptivity cannot, by conservation of energy), so it is not possible to thermally radiate more energy than a blackbody, at equilibrium.
		At thermal equilibrium, the emissivity of a body (or surface) equals its absorptivity.
		More generally, it radiates with some emissivity multiplied by the blackbody formula.
	en.wikipedia.org /wiki/Kirchhoff's_law_(thermodynamics) (1516 words)

	Physics Pedagogical Resources
		First, the fact that Kirchhoff's law for the equality of the absorptivity and emissivity holds not just for the integrated values but also wavelength by wavelength and angle by angle implies that the thermal radiation emitted by a sample is polarized.
		In this document I derive formulas for the interior angle and area of a triangle with sides of equal length on the surface of a unit sphere.
		This is a quick summary of how to derive the angles at which the primary and secondary rainbows for water droplets in air are seen.
	www.usna.edu /Users/physics/mungan/Scholarship/scholarship.html (1516 words)

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