NATURE OF THE RADIATIONS 



63 



and RaC (in the presence of radon) are about 0.05 per cent, 0.5 per cent, 

 and 1.0 per cent greater, respectively, than those corresponding with the 

 equilibrium mixture values of radium shown in Table II— 1. 



-L 



I 



^.-.bt-.Y-radiation 



'•::',;c:'::^ 



Nature of the Radiations 



A sample of radium salt, after radioactive equilibrium has been at- 

 tained, will emit alpha rays, beta rays, and gamma radiation. The alpha 

 rays are rather massive particles carrying a positive charge of electricity ; 

 the beta rays are negative electrons with rather large velocities of ejec- 

 tion. 



To demonstrate these properties put a small sample of radium salt 

 in the bottom of a cylindrical hole in a lead block and then place the 

 block so that the vertically emitted rays pass at right angles through an 

 intense magnetic field furnished by a powerful electromagnet, as shown 

 in Fig. II-4. 



The magnetic lines of force are represented as entering into and per- 

 pendicular to the plane of the paper. It is found that the beta particles 

 are deflected to the right 

 and the alpha particles to 

 the left. The beta particles 

 are observed to move on the 

 arc of a circle while they are 

 in the magnetic field. Their 

 deflection to the right proves 

 them to be negatively 

 charged. The alpha parti- 

 cles are observed to undergo 

 a similar deflection to the 

 left; hence they are posi- 

 tively charged. The rela- 

 tive curvature of the paths 

 depends on their relative 

 values of e/m and velocity, 

 such that Hev = mv 2 /R. 

 Here H is the intensity 

 of the magnetic field, and 

 R the radius of curvature of the circular paths. 



The vertically emitted group of rays, called gamma radiations, suffer 

 no deflection. This lack of deflection shows that they carry no net 

 charge. They have been identified as radiant energy comparable to 

 very short-wave x-rays. 



Fig. II-4. Depicting the deflection of alpha 

 and beta rays in a uniform magnetic field, set per- 

 pendicularly to the paper and directed downward. 

 Gamma rays not deflectable. 



