Max Planck: On the Law of Distribution of Energy in the Normal Spectrum

The recent spectral measurements made by O. Lummer and E. Pringsheim, and even more notablethose by H. Rubens and F. Kurlbaum, which together confirmed an earlier result obtained by H. Beck-mann, show that the law of energy distribution in the normal spectrum, first derived by W. Wien frommolecular-kinetic considerations and later by me from the theory of electromagnetic radiation, is notvalid generally.

In any case the theory requires a correction, and I shall attempt in the following to accomplishthis on the basis of the theory of electromagnetic radiation which I developed. For this purpose it willbe necessary first to find in the set of conditions leading to Wien’s energy distribution law that termwhich can be changed; thereafter it will be a matter of removing this term from the set and making an appropriate substitution for it.

Planck