A proton, a deuteron and an \( \alpha \)- particle with same kinetic energy enter into a uniform magnetic field at right angle to magnetic field. The ratio of the radii of their respective circular paths is:
\( 1:\sqrt{2}:\sqrt{2} \)
\( 1:1:\sqrt{2} \)
\( \sqrt{2}:1:1 \)
\( 1:\sqrt{2}:1 \)