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# Rayleigh-Jeans law

In physics, Rayleigh-Jeans Law, first proposed in the 19th century, expresses the energy density of blackbody radiation of wavelength λ as

$f(\lambda) = 8\pi k\frac{T}{\lambda^4}$

where λ is in meters, T is the temperature in Kelvins, and k is Boltzmann's constant.

The law agrees with experimental measurements for long wavelengths but disagrees for short wavelengths.

Max Planck revised the law, which states:

$f(\lambda) = 8\pi hc \frac{\lambda^{-5}}{e^\frac{hc}{\lambda kT}-1}$

where h is Planck's constant, c is the speed of light.

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