LIII. The photoelectric effect

p ROBABLY there is no line of investigation more likely to lead to a correct understanding of the phenomena of photoelectric action than a careful determination of the relations between the nature of the metal, the frequency of the light, and the kinetic energy of the liberated electrons.A large amount of work has been done in the attempt to determine these relations, hut the results ha~e been very contradictory.For instance, yon Baeyer ~md Gehrts t, and Klages ~ found, in the case of several metals, that the maximmn initial velocity of the electrons was independent of the metal used.Ladenburgw and other physicists have decided that the eleetronegative metals give off electrons with the greatest velocities ; whilst Millikan and Winchester[[ concluded tliat the initial velocity bears no relation to the Volta series.Most physicists who have investigated the subject believe that the maximum initial kinetic energy is a linear function of the frequency of the ]ight ; but some 82 have obtained results supporting the view that the maximmn velocity varies as the first power of the frequency.The results of the present investigation show that there is a much greater unity in the relations between different metals and wave-lengths than b.as hitherto been supposed.In fact, it will be shown that the important features of the photoelectric behaviour of any metal are determined by a single parameter characteristic of the metal.The parameter has the dimensions of a frequency, and its significance will be explained later.The first part of the paper is a discussion of the experimental data.These data may be of value in testing any theory of photoelectric action.In the latter part of the paper the results are applied to test the theories of these effects which have been developed by Einstein ** and by one of the authors t~f.e Communicated by the Authors.