228 



RADIATION UIOLOGY 



made, it is obviously necessary to take into account the problems raised 

 by such factors as the angle of the illuminating cone from the condenser, 

 the probable variations of path Icnj^th, and scatter into or outside the 

 area of measurements as this cone is changed. These questions are con- 



IMAGE OF SOURCE 

 4-nim DIA. HERE 

 31-10-02 OBJECTIVE \ CONDENSER 



SHOULDER 



31-15-02 EYEPIECE 



J. 



DIAPHRAGM 



Fig. 6-9. (a) Diagram of the optical components of a microscope with reflecting- 

 refracting condenser and objective, for use in the visible and ultraviolet spectrum. 

 (The Bausch and Lomb Optical Company.) (b) Diagram of a totally reflecting objec- 

 tive, a design with chromatic correction over a wide extent of the visible, ultraviolet, 

 and infrared regions of the optical spectrum. (Courtesy of A. J. Kavanagh and The 

 American Optical Company.) 



sidered at length, from both the theoretical and experimental viewpoints, 

 in such references as C^aspersson (193G, 1950); Uber (1939); Thoroll 

 (1947); Swift (1950); and Davies and Walker (1953). 



Caspersson, especially, has discussed at some length the problems raised 

 by image formation, a treatment which seems to make the whole ques- 



