Rayleigh–Jeans law
In physics, the Rayleigh–Jeans law is an approximation to the spectral radiance of electromagnetic radiation as a function of wavelength from a black body at a given temperature through classical arguments. For wavelength λ, it is B λ ( T ) = 2 c k B T λ 4 , {\displaystyle B_{\lambda }(T)={\frac {2ck_{\text{B}}T}{\lambda ^{4}}},} where B λ {\displaystyle B_{\lambda }} is the spectral radiance (the power emitted per unit emitting area, per steradian, per unit wavelength), c {\displaystyle c} is the speed of light, k B {\displaystyle k_{\text{B}}} is the Boltzmann constant, and T {\displaystyle T} is the temperature in kelvins.