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Wien approximation

(yields approximation of black body curve useful at short wavelengths)

The Wien approximation is a formula that approximates black-body radiation, converging to the true value (the Planck function) at shorter wavelengths, i.e., a good approximation of one of the two tails of the spectrum. The Wien approximation has the advantage of being a simpler function, easier to manipulate algebraically and incorporate into formulae describing astronomical phenomena. It consists of the Planck function with the denominator's "subtraction of 1" removed: at short wavelengths, this fraction is quite small and such a modification to the denominator affects the total only slightly. The Wien approximation and the Rayleigh-Jeans law are analogous, each approximating one end of a black body spectrum. The Wien approximation formula (in the form based on frequency):

         2hν3    1
B(ν,T) = ———— ————————
          c2  ehν/(kBT)

(function,physics,EMR,black body)
Further reading:
http://en.wikipedia.org/wiki/Wien_approximation

Referenced by pages:
Rayleigh-Jeans law

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