A proton and an α-particle, having kinetic energies Kp and Kα, respectively, enter into a magnetic field at right angles.
The ratio of the radii of trajectory of proton to that of α-particle is 2 : 1. The ratio of Kp : Kα is :
(1) 1 : 8
(2) 8 : 1
(3) 1 : 4
(4) 4 : 1