# Two protons whose velocities are in the ratio $4 : 1$, move perpendicular to a uniform magnetic field, the ratio of the radii of their paths will be

$\begin {array} {1 1} (a)\;1:1 & \quad (b)\;2:1 \\ (c)\;4:1 & \quad (d)\;1:4 \end {array}$

$R = \large\frac{mv}{qB}$
\begin{align*}R_1 = \frac{m_p \times 4v}{qB}; \; \; \; R_2 = \frac{m_p \times v}{qB} \end{align*}
$\therefore R_1 : R_2 = 4 : 1$
Ans : (c)
edited Nov 28, 2017