170 



BIOLOGICAL EFFECTS OF RADIATION 



markedly to longer wave-lengths, and a second maximum appears of 

 almost coordinate magnitude in the region of maximum absorption. Of 

 course, a similar difficulty will be encountered wherever filters produce 

 a relatively impure spectrum. In a case where the absorption coefficient 

 of the material irradiated is known, an interpretation may be arrived at, 

 but in cases where one is irradiating a biological material of unknown 

 absorption coefficient, the difficulties of interpretation become aggravated. 



REFLECTORS 



In the course of the construction of equipment, it is often desirable 

 to select suitable materials for reflecting radiation. As a convenience, 



4> 



0) 

 D- 



100 

 90 

 80 

 70 

 60 

 50 



40 

 <u 



^ 30 

 o 



'i 20 



^ 10 

 



2000 2400 2800 3200 3,600 4,000 4,400 4,800 5,200 5,600 ^000 



Wave-Length (A.U) 



Fig. 15. — Reflectance of polished metals. {Luckiesch, 47.) 



2,000 2,400 2.800 

 Fig. 16 



J.200 3600 4,000 4,400 4,800 5,200 5,600 6,000 

 Wave Length (A.U) 

 Reflectance of dry powders. (Luckiesch, 47.) 



therefore, we are including curves of reflectance, the monochromatic 

 determination of reflectance for wave-lengths varying from 2000 to 

 6000 A. Where one wishes to obtain specular reflection. Fig. 15 (47) shows 

 the types of metals available for construction of reflectors. More 



