8 



BIOPHYSICALLY ACTIVE X-RAYS 



and occasionally molybdenum targets are used, the discussion will be 

 limited to the emissions from these two metals. 



0.4 

 Wavelength in A 



/5 2 0,«1«2 



K series 



Tungsten 



j_ 



123.5 



41.2 30.9 24.7 



Comparable kv-peak voltage (V p ) 



20.6 



_L 



L series at — *• 

 1.0 to 1.7 A 



17.6 



Fig. 1-4. These curves show the general radiations from a tungsten target. The 

 value of the maximum at the peak of each curve moves to longer wavelengths as 

 the exciting kilovoltage is reduced. The glass bulb if 1 mm thick transmits about 

 25 per cent of the 1-A wavelength emitted. The attached characteristic line spec- 

 trum of the K series shows relative positions of these emissions with respect to the 

 general radiation curves. (Curves after C. T. Ulrey [1918].) 



Figure 1-4 shows the intensity of emission of the x-radiations at 

 different wavelengths from a tungsten target bombarded by electrons 

 which had been accelerated by various voltages across a Coolidge tube. 



