CHAPTER IV 



Reflected-liglit Microscopy 



1. METHODS APPLIED IN REFLECTED-LIGHT MICROSCOPY 



The illumination arrangement in reflected-light microscopes difters 

 from that of transmitted-light microscopes. Figures 4.1 and 4.2 show 

 the two principal arrangements. 



In Fig. 4.1 the light originated by the source 5 is reflected by the 45"" 

 slanted semi-reflecting plate G (Beck illuminator), then passes through 



Fig. 4.1. Illumination with a semi-reflect- 

 ing plate G. 



Fig. 4.2. Illumination with a mirror M. 



the objective Ox-, is reflected back by the object P to the objective 

 and passes through the plate in direction of the eyepiece. 



The whole aperture of the objective is used; yet, the luminous 

 flux reaching the eyepiece cannot exceed the theoretical 25 per cent 

 maximum of the incident flux. 



Figure 4.2 shows another illuminating arrangement comprising 

 the mirror M, which occludes half of the objective's available aperture. 

 One half of the objective serves as condenser, the other half as ob- 

 jective. This entails, hence, reduced definition. Furthermore, this 

 arrangement exhibits an oblique illumination which may bring about 



129 



