On the Distribution of Energy in the Emission Spectrum of a Blackbody;
by Willy Wien
Even though the shift in the radiation of a blackbody with temperature, and the distribution over all wavelengths can be derived on the basis of the electromagnetic theory of light in a purely thermodynamic way without the help of any special hypotheses, It has not yet been possible to determine the distribution of the energy itself. And yet it is in the nature of things that the dependence of the intensity on the wavelength should also be completely determinable through the properties of the radiation itself, because it depends only on the temperature and not on the special properties of individual bodies.
The radiation of a blackbody corresponds to the state of thermal equilibrium and consequently to a maximum of entropy. For example, If a process were known by which the wavelengths could be changed in a manner such that the entropy increases without an expenditure of work and without absorption, then the distribution of energy in the spectrum of a blackbody would be completely determined from the condition of maximum entropy. As I have shown in an earlier work, it is always possible to state the entropy of radiation of known intensity and color, but for the time being there are no known physical processes that would cause such a change in color. It is therefore not possible to determine the energy distribution without hypotheses.
An attempt to base a complete law of radiation on certain assumptions was made by E.v. Lommel [1] and W. Michelson [2]. The latter makes the following prerequisites:
- ↑ E.v. Lommel, Wied. Ann. 3. p. 251. 1877.
- ↑ W. Michelson, Journ. de phys. (2) 6. 1887.
