Particle Entropies and Entropy QuantaII. The Photon Gas

Abstract

We consider a photon gas, which is enclosed in a cavity and is in thermal equilibrium at temperature T. Each photon has a particle entropy σ = ka and a particle energy ε = hv = cp. The particle entropy σ is measured by the dimensionless number a in multiples of the Boltzmann constant k, which serves as an atomic entropy unit. The particle energy ε is related to the frequency Þgn and the momentum p of the relativistic photons, c velocity of light. Particle entropy and particle energy are connected by the temperature, ε = σT. Applying statistical thermodynamics we obtain the thermodynamics of the photon gas, written in particle entropies a. We also get the Planck distribution, and the Planck, Stefan-Boltzmann, and Wien radiation law. - The total entropy S of the photon gas is composed of two parts S