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Maxwell's Law, and the Absorption and Emission of Radiation

Published online by Cambridge University Press:  24 October 2008

E. A. Milne
Affiliation:
Trinity College

Extract

In the famous paper in which he developed his theory of radiation, Einstein investigated two problems. He investigated first the problem of what distribution of radiant energy in the steady state would be set up by an enclosed assembly of atoms in thermodynamic equilibrium radiating and absorbing according to the assumptions of his theory; he showed that the distribution so set up was given by Planck's law. He investigated secondly the velocities set up amongst the atoms in consequence of the random variations in direction of the emissions and absorptions; provided that emissions are assumed to be directed, so giving rise to recoil momentum, he showed that the mean square velocity-component in a given direction, , is equal to its equipartition value, given by .

Type
Articles
Copyright
Copyright © Cambridge Philosophical Society 1926

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References

* Phys. Zeit. vol. 18, p. 121, 1917.Google Scholar

It is assumed that ν is small compared with the velocity of light, c.Google Scholar

* Ann. d. Phys. vol. 43, p. 810, 1914.Google Scholar

Berlin Sitz. p. 324, 1917.Google Scholar

* I am indebted to Professor Eddington for the proof of this.Google Scholar

* Monthly Notices, R.A.S. vol. 86, p. 578, 1926.Google Scholar