144 



The Electron Microscope 



Fig. 52. Airy figure 



first image. 



recur focal _ 

 plane,.-^^ 



objective,: 



dip fro c ted beorn\^ W/ 

 object, (gracing) Jp«C-^ 



ilJummatrng beom.-. 



Fig. 53. Abbe's theory 



order diffracted beams can enter the objective. This gives for 

 the finest detail resolvable with a given objective 



I ' I 



dA 



2 sin a 

 which is usuallv called the Abbe limit. 



(59) 



