APPLICATIONS AND SOURCES OF ULTRAVIOLET 



59 



CONVERSION FACTORS 

 POWER, INTENSITY AND DISTANCE, AND WORK AND ENERGY 



The use of metric and U.S. units, separately and together, named units, 

 and various time units, with little standardization of practice, requires 

 frequent use of conversion factors. In Table 2-4 are listed various con- 



Table 2-4. Conversion Factors 



From 



Multiply by 



To 



Power Output and Intensity 



UV watts output, total 



UV watts output, total 



UV pw/cm^ 



UV output /steradian 



UV output/steradian 



UV output/steradian 



UV intensity, unit area, 1 meter , 

 UV intensity /cm^ at 1 meter. . . . 



ergs /sec 



joules /sec 



10.0" 

 0.001 

 . 929 



10.0" 

 0.01 

 0.0001 

 0.176 



10 X 103 

 0.1 

 1.0 



UV Mw/cm^ at 1 meter 

 UV juw/sq ft at 10 ft 

 UV mw/sq ft 

 UV output total 

 UV output/cm^ at 10 cm 

 UV output /cm 2 at 1 meter 

 UV intensity, unit area, 10 ft 

 UV intensity /sq ft at 10 ft 



UV MW 



UV watts 



Work and Energy* 



joules 



joules 



ergs 



ergs 



g-cal 



Btu 



r (roentgens) in air 



Photons or quanta at 2536 A. 



1.0 



0.01665 X 10« 



0.1 



0.011665 

 69.77 X 10' 

 17.4 X 106 



0.00018315 



0.0131 X 10 '2 



UV watt-sec 

 UV /iw-min 

 UV MW-sec 

 UV MW-min 

 UV /Ltw-miu 

 UV /iw-min 

 UV MW-min 

 UV MW-min 



Exposures 



joules /cm 2. 

 ergs /cm 2. . 

 g-cal /cm 2 . 

 r/cm^ 



0.01665 X 106 

 0.001665 

 69.77 X 103 

 0.00018315 



UV MW-min/cm^ 

 UV nw-min/cm^ 

 UV MW-min/cm^ 

 UV MW-min/cm^ 



" Approximate. 



^ When on equal areas — exposures. 



versions to the centimeter-microwatt-minute units used in this chapter. 

 The relation between ultraviolet output and maximum intensity refers 

 only to essentially linear sources, to distances greater than the length of 

 the source, and to directions of maximum intensity perpendicular to the 

 center of the source. Energy per steradian refers only to the steradian in 

 that maximum intensity direction and, literally, only to a very small part 

 of the solid angle represented by the steradian. For this reason, energy 



