A proton, a deuteron and an αparticle accelerated through the same potential difference enter a region of uniform magnetic field, moving at right angles to B. What is the ratio of their K.E.?

K.E. gained by charged particle of charge q when accelerated under a potential difference V will be Ek=qV.For a given V, E∝q.For proton, deuteron and α -particle, the ratio of charges is 1: 1: 2