Iv] NATURE OF THE RADIATIONS 107 
d, of the ray parallel to the field after traversing a distance / is 
given by 
On leaving the electric field, the particle travels in the direction of 
the tangent to the path at that point. If @ is the angular deviation 
of the path at that point 
eX 
tan 0= —.. 
9 
nw? 
The photographic plate was a distance h above the extremity of 
the field. Thus the particles struck the plate at a distance d, from 
the original path given by 
d,=h tan @+ d, 
BN 5 
mv 

In the experimental arrangement the values were 
d, = “4 cms. ; 
AC = IO Se MOB e 
l= 3°45 cms. ; 
h=1-2' cms. 
If the radius R of curvature of the path of the same rays is ob- 
served in a magnetic field of strength H perpendicular to the rays, 
je tae 
Go JER. 
Combining these two equations we get 
xX. (5 ae n) 
Jal 513. Gb 
A difficulty arose in identifying the radiations for which the 
electric and magnetic deviations were determined. Becquerel 
estimated that the value of HR for the rays deflected by the 
electric field was about 1600 c.G.s. units. Thus 
Y= 
v=1°6 x 10" cms. per second, 
and foe 10’. 
m 
