314 Kunz — Electromagnetic Emission Theory/ of Light. 



but i'or tlic rjcneral law of radiation, and especially for short 

 wave kMigtlis, c'onsidtM'al)lediiKcultiesliave been encountered by 

 every investii;;ator. Planck in tlie theory of radiation assumes 

 that the resonators gain or lose energy, not quite gradually by 

 infinitely small amounts, but only by certain portions of a 

 dc'tinite finite magnitude. The portions of energy depend on 

 the frequency n of the resonator, so that 



E = hn. 



Planck's law shows a remarkable agreement with the experi- 

 mental results and allows the determination of the funda- 

 mental quautities of nature; yet the mechanism of radiation is 

 not revealed by the theory ; it seems to me, that the resonators 

 have but little analogy with the motions of the electrons in 

 metals, which lead us to assume a connection between Roiit- 

 gen rays and light. Moreover as far as our present knowledge 

 goes, we have no experimental evidence of portions of electro- 

 magnetic energy of the form hn ; the experiments made on the 

 photoelectric effect of sodium-potassium alloy, made by the 

 author, show that the kinetic energy of the electrons emitted 

 by this alloy is for a considerable range proportional to the 

 square of the frequency of the incident light. On the other 

 hand, it is well known that the optical properties of metals 

 cannot be deduced quantitatively with any degree of accuracy 

 from the electrical properties. It has been shown, however, 

 by Hagen and Rubens that rays of light of wave length 

 between 8 and 25 fi are absorbed to a degree that may be 

 calculated with considerable accuracy from the conductivity. 



H. A. Lorentz has based a theory of thermal radiation on this 

 fact, which, however, is restricted to long wave lengths and 

 coincides with the formula given above. This theory has been 

 extended to short waves by J. J. Thomson, and I have shown 

 what would be the acceleration of the electron in the case of 

 collision with an atom.. I came also to the conclusion that the 

 energy of a monochromatic beam of light is proportional to 

 the square of the frequency, a result which seems to agree 

 with the present experiments. 



Whereas the principle of relativity and the theory of radia- 

 tion of Planck assume discontinuities in the emission and 

 absorption of light, there are many optical phenomena pointing 

 towards a corpuscular constitution of light and Rdntgen rays. 

 This is so much so, that a special corpuscular theory of Ront- 

 gen rays has been developed by Bragg, who considers them as 

 made up of doublets of positive and negative particles. The 

 main facts in the line of his argument are as follows : The 

 number of atoms in a gas ionized by Pontgen rays is exceed- 

 ingly small, while we should expect that all the atoms struck 



