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ELECTRON- 

 MICROSCOPIC 

 ANALYSIS 



Carl A. Moore 



Ability to discriminate among minute objects that lie very close together 

 is described as the resolving power of a microscope. In spite of various methods 

 that may be employed to increase the resolving power of a light microscope, ob- 

 jects separated by less than 0.1 micron (0.0001 millimeter) cannot be resolved. 

 Thus it is that the limits of the light microscope are not the lack of skill on the 

 part of the designer but rather are due to the light — the media used for observa- 

 tion. 



This limitation of the light microscope is an important factor in microscopy ; 

 for example, the study of viruses must be conducted with particles and separa- 

 tions much smaller than this, and the study of colloids necessitates greater re- 

 solving power than that possible with the light microscope. 



With the introduction of the electron microscope, this limit on resolving 

 power has been greatly decreased, since the magnification is no longer limited 

 by the wave length of visible light. Theoretically, the electron microscope should 

 be capable of resolving powers as small as atomic dimensions. In actual prac- 

 tice, however, the microscope has not been perfected to that extent. Neverthe- 

 less magnifications of over 100,000 diameters are practical with the electron 

 microscope, as compared with a useful limit of 2000 diameters for the light 

 microscope. 



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