Planck's Law

Planck's law gives the spectral radiance emitted by a blackbody in thermal equilibrium as a function of wavelength (or frequency) and absolute temperature, quantitatively expressed by B_λ(T) = (2hc^2/λ^5)·[1/(exp(hc/(λkT)) − 1)] (or its frequency-domain analogue), describing how emitted intensity varies across the spectrum.