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spectra. It was found that the line spectra was materially changed when 

 the center in question was placed in a strong magnetic field. Later this 

 was shown to be related to the vibration of a negative charge of small 

 magnitude, giving additional confirmation of the electron theory of radiation. 

 We know that when a particle or particles of matter execute some form of 

 simple harmonic motion with sufficient frequency that a note of definite 

 pitch is produced. Why can not we carry the sound analogy over into the 

 realm of electronic motion and conceive of one of these electrons executing 

 some form of simple harmonic motion with, of course, some definite period, 

 its frequency bearing some definite relation to its temperature, as proposed 

 by Planck. 



If the sound analogy referred to applies to combined waves of varying 

 frequency and wave length so as to produce "spectral harmonics'' to coin 

 such a phrase, the center producing them must of necessity be very complex. 

 Take for instance the fluorescent effects noted when the vapors of certain 

 metals is examined; or the luminosity of a gas when a small portion of its 

 molecular aggregate has been ionized. It has been found that when 

 10 ooo ooo P art °^ ^ e m °l eeu l es °f a S as has been ionized that it becomes 

 luminous. Likewise it has been observed that dissociation of some of the 

 halogen group is accompanied by changes in its absorption spectrum. Many 

 experiments also show that fluorescence and likewise phosphorescence are 

 due to or accompanied by dissociation or ionization. 



Considerable light has been shed upon this problem by the study of the 

 emission of heat by radioactive substances. Curie and Laborde found in 

 1903 that the temperature of a radium compound was maintained by itself 

 several degrees higher than its surroundings. It was found that radium 

 emitted heat at a rate sufficient to more than melt its own weight of ice 

 per hour. According to Rutherford the emission of heat from radioactive 

 substances is a measure of energy of the radiation expelled from the active 

 matter which are absorbed by itself and the surrounding envelope. This 

 heating effect was supposed to be a measure of the kinetic energy of the 

 expelled a particles; the heating effect was calculated by determining the 

 kinetic energy of the a particles expelled from one gram of radium per 

 second. 



K.E. = I mn SV 2 m = mass of particle. 



n = no. emitted by each group per second. 



v = the velocity of the different, group of particles 



