Chapter Q 



The Microscope 



The Compound Microscope 



The ordinary laboratory microscope uses brightfield illumination 

 Avith direct light furnished by a substage condenser and mirror. The 

 image of the specimen appears on a l^right, well-lit field. 



Diagrams designating all the parts of a microscope are provided by 

 the manufacturers and will not be included here; we will, however, give 

 a brief listing of the important parts and pertinent information con- 

 cerning their use. 



The lenses of a microscope are the oculars (eyepieces) at the top and 

 the objectives at the bottom of the body tube. The objectives magnify 

 the specimen a definite amount, forming an image which is again mag- 

 nified by the ocular eyepiece. The lenses of a good microscope should 

 not only magnify, but also should improve the visible detail. This is 

 the resolving power and is a function of (1) the wave length of the light 

 used, (2) the lowest refractive index (refractive index is a measurement 

 of the refraction or bending of light rays as they pass through from one 

 medium to another and at an oblique angle) between the objective and 

 tlie substage condenser (page 90), and (3) the greatest angle between 

 two rays of light entering the front lens of the objective. Blue light 

 increases resolving power over white light, ultraviolet increases it e\en 

 more, but cannot be seen and results must be photographed. 



Oculars are manufactured in a variety of powers of magnification 



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