Question

A proton and an $\alpha -$particle enter a uniform magnetic field at right angles to it with same velocity. The time period of $\alpha -$particle as compared to that of proton, will be

• A. four times
• B. two times
• C. half
• D. one-fourth

Answer 1

The correct option is B two times

Time Period $T=\frac{2\pi m}{qB}$
$\therefore \frac{T_{alpha}}{T_{proton}}=\frac{m_{alpha}}{m_{proton}}\times \frac{q_{proton}}{q_{alpha}}=\frac{4}{1}\times \frac{1}{2}=2$