246 



RADIATION BIOLOGY 



luminous intensity or color temperature. The box is smaller than the 

 enclosure recommended by the U.S. National Bureau of Standards 

 (Coblentz and Stair, 1933), but the error introduced is small. It is 

 painted flat black on the interior and has suitable openings for venti- 

 lation. In the front is a 10- by 15-cm aperture with a sliding shutter 



RADIOMETRIC 



STANDARD 



LAMP 



50 w 



PHOTOMETRIC 



OR 



COLOR TEMPERATURE 



STANDARD 



500 w 



STANDARD LAMP POWER CIRCUITS 



Fig. 3-40. Diagram of a housing for standard lamps, 

 circuits for powering the lamps are shown. 



Suitable voltage-regulated 



that can be opened and closed without bringing the operator's hand into 

 line with the detector. The detector to be calibrated is mounted in front 

 of the cabinet at a distance of 2 m from the standard lamp. 



Radiant Intensity. The secondary standard of radiant intensity, as 

 routinely issued by the U.S. National Bureau of Standards {ibid.) is a 

 nominal 50- w 115-v carbon-filament vacuum lamp that has been cali- 



