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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Stefan–Boltzmann law ： ウィキペディア英語版 Stefan–Boltzmann law The Stefan–Boltzmann law, also known as Stefan's law, describes the power radiated from a black body in terms of its temperature. Specifically, the Stefan–Boltzmann law states that the total energy radiated per unit surface area of a black body across all wavelengths per unit time (also known as the black-body ''radiant exitance'' or ''emissive power''), $j^$, is directly proportional to the fourth power of the black body's thermodynamic temperature ''T'': :$j^\; =\; \backslash sigma\; T^.$ The constant of proportionality σ, called the Stefan–Boltzmann constant or Stefan's constant, derives from other known constants of nature. The value of the constant is :$$ \sigma=\frac= 5.670373 \times 10^\, \mathrm}, where k is the Boltzmann constant, h is Planck's constant, and c is the speed of light in a vacuum. Thus at 100 K the energy flux is 5.67 W/m2, at 1000 K 56,700 W/m2, etc. The radiance (watts per square metre per steradian) is given by :$L\; =\; \backslash frac.$ A body that does not absorb all incident radiation (sometimes known as a grey body) emits less total energy than a black body and is characterized by an emissivity, : :$j^\; =\; \backslash varepsilon\backslash sigma\; T^.$ The irradiance $j^$ has dimensions of energy flux (energy per time per area), and the SI units of measure are joules per second per square metre, or equivalently, watts per square metre. The SI unit for absolute temperature ''T'' is the kelvin. ''$\backslash varepsilon$'' is the emissivity of the grey body; if it is a perfect blackbody, $\backslash varepsilon=1$. In the still more general (and realistic) case, the emissivity depends on the wavelength, $\backslash varepsilon=\backslash varepsilon(\backslash lambda)$. To find the total power radiated from an object, multiply by its surface area, $A$: :$P=\; A\; j^\; =\; A\; \backslash varepsilon\backslash sigma\; T^.$ Wavelength- and subwavelength-scale particles, metamaterials,〔("Beyond Stefan-Boltzmann Law: Thermal Hyper-Conductivity." ) 26 September 2011.〕 and other nanostructures are not subject to ray-optical limits and may be designed to exceed the Stefan–Boltzmann law. ==History== The law was deduced by Josef Stefan (1835–1893) in 1879 on the basis of experimental measurements made by John Tyndall and was derived from theoretical considerations, using thermodynamics, by Ludwig Boltzmann (1844–1906) in 1884. Boltzmann considered a certain ideal heat engine with light as a working matter instead of gas. The law is highly accurate only for ideal black objects, the perfect radiators, called black bodies; it works as a good approximation for most "grey" bodies. Stefan published this law in the article ''Über die Beziehung zwischen der Wärmestrahlung und der Temperatur'' (''On the relationship between thermal radiation and temperature'') in the ''Bulletins from the sessions'' of the Vienna Academy of Sciences. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Stefan–Boltzmann law」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.