554 



Microscopy /29 : 8 



filament and accelerated through a high potential, perhaps 50 kilovolts. 

 This is equivalent to producing light photons from a heated filament 

 (except that the electrons are monochromatic and the photons are not). 

 The photon and electron beams are then collimated by lenses, pass 

 through the object, and are magnified by an objective lens and finally 



as 





\ 

 " n -^" 



Figure I I. A crystal of the rhombic type of tobacco necrosis 

 virus in which the molecular order is unusually good, x 84,000. 

 After L. W. Labaw and R. W. G. WyckofT, "The Electron 

 Microscopy of Tobacco Necrosis Virus Crystals," J. Ultra- 

 structure Research 2: 8 (1958). 



by a projector (or eyepiece lens). The image so formed is suitably 

 detected. 



Electrons are more highly absorbed when going through a solid 

 specimen than are photons of visible light. Even a glass cover slide 



