Wien Approximation - Relation To Planck's Law

Relation To Planck's Law

The 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 However, it was soon superseded by Planck's law, developed by Max Planck.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.