Zero-point term in cavity radiation

Abstract

We show that if one accepts the reality of a zero-point term (1/2)h/ω per normal mode in the spectral distribution of cavity radiation, then the Planck law can be derived with no further nonclassical assumptions; we do this in two different ways, both based on Einstein’s work at the beginning of the century. The argument is intuitive and clarifies some conceptual difficulties; we point out where more elaborate theoretical work is required. A related derivation of the Planck law due to Boyer is examined.