DESCRIPTION OF THE Figure 8-1 is a comparison of the optical 



MICROSCOPE microscope with the electron microscope show- 



ing equivalent parts: magnetic fields are 

 equivalent to lenses; both have specimen levels; and both have photographic 

 plates for pictures. For comparison, the electron microscope is diagrammed up- 

 side down. 



A simplified drawing of the R.C.A. compound magnetic electron microscope, 

 type EMB, is shown in Figure 8-2. Focusing is accomplished by varying the 

 lens power. The specimen mount is the movable stage. As the stage is inside 

 the vacuum portion of the microscope, it is moved by means of fine screws and 

 a metal flexible bellows. 



The electron beam is concentrated on the specimen by the magnetic field 

 produced in the condenser-lens coil. After passing through the specimen, the 

 electrons are focused by the objective-lens coil into an intermediate image, and 

 the projection-lens coil produces a further magnified image on the fluorescent 

 screen in the final viewing chamber. 



To facilitate the initial adjustment of the specimen, a port is provided for 

 viewing the intermediate image on a fluorescent screen close to the plane of the 

 projection-lens coil. By virtue of the relatively low magnification at this point, 



OPTICAL 

 MICROSCOPE 



ELECTRON 

 MICROSCOPE 



Phoioqrophic Plate 



Eyepiece or 



Photo -projector 



Objective Lens System 



Substage Condenser 



Reflector 



Projected 

 Imoge 



Photogroph'C Plate 



Magnetic Co>l 

 Projector 



*zzz>, 



1 III 



II 



Magnetic Coil 

 Serving as 

 Objective 



Magnetic Coil 



Concentrotmg 

 Electron Beam 



-•£ Source 



'I >• / V 



Light-' v Electron 



K 



Figure 8-1. Comparison of light microscope and magnetic electron microscope. 



(Burton and Kohl) 



142 



