﻿Absorption of Homogeneous /3 Rays. 



729 



Hp = 1380 to Hjo = 11500 gauss cm. Curves for slower rays 

 are shown in fig. 3, and for faster rays in fig. 4. j3 particles 

 could, however, be detected with certainty up to Hp = 16000, 

 when they were so swift as to be able to pass through more 

 than 1 cm. of aluminium. Readings at this point were 

 inconvenient on account of the high currents in the magnet- 

 coils necessary to produce the required field. 



Fio-. 4. 



JOO» 



•4- -6 



GRAMS PEE? 



CM? 



By producing the linear part of curve CO (fig. 2) to cut 

 the axis of D, we get the thickness of matter, OD, which 

 would be traversed by the /3 particles if the law of absorption 

 had continued as in the linear part of the curve. The 

 distance OD might, on analogy of the Bragg a-ray curves, 

 be called the " range " of the /3 particle in aluminium. It 

 gives the thickness of aluminium in which most of the 

 /§ particles are stopped. Such a quantity may prove useful 

 in some experiments in deducing the velocity of /8 rays 

 from absorption curves. A curve showing the range of 

 jS rays in aluminium at various velocities is given in 



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