74 AN ELEMENTARY THEORY OF PHASE MICROSCOPY 



increase in the relative energy content is not important except with the 

 B-type objective. It can be shown that the main effect of the increased 

 relative energy content in the diffraction rings is to offset the degree of 

 contrast obtained in the phase microscope. 



The above considerations indicate that no marked loss of resolution 

 is to be expected with the use of a phase microscope provided that the 

 diffraction plate has been chosen so as to obtain the most favorable 

 compromise between contrast and resolution. In general, this con- 

 clusion is in accord with experiment. It is well to bear in mind, how- 

 ever, that the resolution of two particles depends on the dimensions and 

 optical properties of the particles as well as on the properties of the 

 diffraction plate. Consequently, sweeping generalizations about the 

 relative resolutions possible with two different diffraction plates or 

 between a phase microscope and an ordinary microscope should be 

 regarded with skepticism. 



