Stefan-Boltzmann constant
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The Stefan-Boltzmann constant (also Stefan's constant), a physical constant denoted by the Greek letter σ, is the constant of proportionality in the Stefan-Boltzmann law: the total energy radiated per unit surface area of a black body in unit time is proportional to the fourth power of the thermodynamic temperature.
The value of σ is 5.670 400(40)×10−8 W·m-2·K-4. This value is derivable as well as experimentally determinable; see Stefan-Boltzmann law.
σ can be defined in terms of the Boltzmann constant <math>k_{\mathrm B}</math> as:
- <math>\sigma = \frac{2\pi^5k_{\mathrm B}^4}{15h^3c^2} = \frac{\pi^2k_{\mathrm B}^4}{60\hbar^3c^2},</math>
where h is Planck's constant, <math>\hbar = h/2\pi</math>is Dirac's form of Planck's constant, and c is the speed of light in a vacuum.
A related constant is the radiation constant ([1]) which is equal to
- <math>\frac{4\sigma}{c}</math>.fr:Constante de Stefan-Boltzmann
ja:シュテファン＝ボルツマン定数 nl:Constante van Stefan-Boltzmann sl:Stefanova konstanta
