Question

An $\alpha$ -particle and a proton enters a perpendicular uniform magnetic field. The period of revolution of $\alpha$ -particles as compared to that of proton is

• A. $2$
• B. $3$
• C. $4$
• D. $1$

Answer 1

Answer: (A)

$2$

Charge of $\alpha$ particle is twice that of proton.
Mass of $\alpha$ particle is $4$ times that of proton.

$T=\frac{2\pi m}{qB}$

$\frac{T_{\alpha }}{T_p}=\frac{m_{\alpha }}{m_p}\frac{q_p}{q_{\alpha }}=4\times \frac{1}{2}$