ILLUMINATION AND PHOTOMETRY 



the coefficient of reflection It is the ratio of the light emit toil 

 to the litfht received and is aways less than unity. Below are 

 given the coefficients of reflection for various well-known surfaces. 



COEFFICIENT OF REFLECTION l 



New aluminum bronze (unprotected) 



Polished brass 



Baked white enamel (paint) 



Matt surface, porcelain enamel 



Silvered mirror 



White matt surface paper (smooth) 



Light buff surface paper (smooth) 



Kmbossed gilt paper 



Light-blue paper 



PEB CENT. 

 REFLECTION 



...54 

 ...60 

 . . 72 

 ...79 

 ... 83 

 ...57 

 . . . 45 

 ...43 

 . 12 



185. Light Distribution. Light, from sources such as incandes- 

 cent lamps, arc lamps, etc., varies in intensity in different direc- 



135 c 



150 165 ISO 165 



120 



60 



46- 80- 15 J 15 J 30 



Flo. 379. Distribution of li^ht-intcnsity about a Hi-ruinllrpi.wrr. <-:irbon- 



The distribution depends not only on the li^ht | 



itself but also on the reilertors, refractors :md fixtures which 

 :ire used with the BOUTOe. In most li^lit smiives the liiihl giving 



element i- BO de-intied tli.-it th- -\\i\\ inten-ity i> ne.-irly tlie 



sMine in ;dl dil Thif i ilarly true of innnnl- 

 lani})s and of &It Ian 



nandard Handbook," Section 14. 



