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## Wien approximation
## Additional recommended knowledge
The law may be written as where *I*(ν,*T*) is the amount of energy per unit surface area per unit time per unit solid angle per unit frequency emitted at a frequency ν.*T*is the temperature of the black body.*h*is Planck's constant.*c*is the speed of light.*k*is Boltzmann's constant.
This equation may also be written as where ## Relation to Planck's lawThe Wien approximation was originally proposed as a description of the complete spectrum of thermal radiation, although it failed to accurately describe long wavelength (low frequency) emission. However, it was soon superseded by Planck's law, developed by Max Planck. Unlike the Wien approximation, Planck's law accurately describes the complete spectrum of thermal radiation. Planck's law may be given as The Wien approximation may be derived from Planck's law by assuming . When this is true, then and so Planck's law approximately equals the Wien approximation at high frequencies. ## Other approximations of thermal radiationThe Rayleigh-Jeans law developed by Lord Rayleigh may be used to accurately describe the long wavelength spectrum of thermal radiation but fails to describe the short wavelength spectrum of thermal emission. ## References**^**J. Mehra, H. Rechenberg (1982). "1",*The Historical Development of Quantum Theory*. New York: Springer-Verlag.__ISBN 0-387-90642-8__.- ^
^{a}^{b}^{c}^{d}R. Bowley, M. Sánchez (1999).*Introductory Statistical Mechanics*, 2nd edition, Oxford: Clarendon Press.__ISBN 0-19-850576-0__. - ^
^{a}^{b}^{c}^{d}G. B. Rybicki, A. P. Lightman (1979).*Radiative Processes in Astrophysics*. New York: John Wiley & Sons.__ISBN 0-471-82759-2__. **^**Equation derived using u=4π/c; see Rybicki, Lightman (1979) reference.
Categories: Statistical mechanics | Foundational quantum physics |

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Wien_approximation". A list of authors is available in Wikipedia. |