# Which of the following particles will have minimum frequency of revolution when projected with the same velocity perpendicular to a constant magnetic field?

$\begin {array} {1 1} (a)\;Electron & \quad (b)\;proton \\ (c)\;He^+ & \quad (d)\;Li^{++} \end {array}$

Angular frequency = $\large\frac{speed}{2 \pi R}$
Minimum angular frequency corresponds to maximum radius
$\large\frac{m}{q}$ ratio is maximum for $He^+$
Ans : (c)