24 The Electron Microscope 



tron will distribute itself over the photographic plate according 

 to this law. One electron can appear only in one spot and can 

 react only with one photographic grain or at most with a few, by 

 secondary effects. If we expose the plate long enough, the 

 density will gradually approach the calculated distribution. This 

 is the essence of the statistical interpretation of wave mechanics, 

 according to M. Born. The intensity distribution is a statistical 

 law, which, if the numbers involved are large enough, will be 

 very closely satisfied by the electrons, in the same way as gas 

 molecules fulfill the gas laws, or human beings — often rather un- 

 willingly — fulfill the laws of mortality statistics. 



