GENERATION, CONTROL, AND MEASUREMENT 



product of wave length and frequency: 



c = v\, or \ = c/v, 

 where c 



131 



(3-1) 



velocity of electromagnetic waves in a vacuum, 2.998 X 

 10^" cm/sec, 

 V = frequency, waves per second, and 

 X = wave length, centimeters per wave. 

 The three most commonly used units of wave length in the visible and 

 near-visible regions are the micron, the millimicron, and the angstrom. 

 Their relations to the millimeter and the meter are: 



micron, n 



millimicron, m/x 



angstrom, A 



1m 

 1 m/x 



10"'' mm 

 10~^ mm 

 10~^ mm 

 1000 m/x 

 10 A 



= 10- 



m 



10-8 m 



10- 



10 



m 



= 10,000 A 



Table 3-3. Comparison of Spectral Units of Radiant Energy 



The micron is employed usually in the infrared and occasionally in the 

 visible; the millimicron and angstrom are used principally in the visible 

 and ultraviolet. The angstrom is employed more commonly by physi- 



