28.5 



region beyond the visible red. To satisfy these conditions Professor Max 

 Planck proposed a modification as follows: 



C X~ 5 



C and c are constant. 



E = c where <p base of natural log. 



<p ex - 1 



As far as recent determinations have been carried out, this laAV holds true 

 and gives practically a complete energy curve of a black body for desired 

 temperatures. Xot only did the statement of this law serve to reconcile 

 purely theoretical conclusions with experimental determinations but paved 

 the way for a more advanced step toward the explanation of the mechanism 

 involved in radiation. 



It is evident that we have yet to establish the connecting link between 

 the thermal condition of a body and the radiant energy sent out into space 

 by that body. If we go back to the theoiy developed by Maxwell we can 

 easily see how this energy is propagated when once started in the ether. 

 This theory clearly accounts for its speed, for interference and diffraction 

 phenomena, but it apparently fails to closely associate thermal condition 

 and the subsequent radiant energy. Planck found that this formula did not 

 satisfactorily represent the relation existing between the frequency and the 

 amount of energy involved, i. e. why, as a body grows hotter, does its color 

 change from dull red to yellow and then white, unless there was some definite 

 mathematical relation existing between the frequency and amount of energy 

 given out by each vibratory particle. In an endeavor to determinejthis 

 relation, Planck was led to advance the Quantum theory or hypothesis wherein 

 he develops a type of function which apparently agrees with the facts better 

 than any theories previously held. In doing this he has made a unique 

 assumption, leaving the idea of the equi— partition of energy so necessary 

 to the former theories, he has put forth the idea of the distribution of energy 

 among the molecules of a substance through a mathematical consideration 

 of probability. It is interesting to note in this connection that Planck states 

 that the reason why no absolute proof of the second law of thermo-dynaniics 

 has ever been given is that it rests not on unchangeable mathematical 

 relations, but upon mere probability or chance. Following out this idea he 

 assumes that there may not be a steady, uniform flow of energy from a 

 heated body, but that this may be propeUed outward in quantities which 



