Question

An $\alpha$ particle and a proton travel with same velocity in a magnetic field perpendicular to be the direction of their velocities, find the ratio of the radii of their circular path

• A. $4:1$
• B. $1:4$
• C. $2:1$
• D. $1:2$

Answer 1

The correct option is C $2:1$

$r=\frac{mv}{qB}\Rightarrow \frac{r_{\alpha }}{r_p}=\frac{m_{\alpha }}{m_p}\times \frac{q_p}{q_{\alpha }}=\frac{4}{1}\times \frac{1}{2}=\frac{2}{1}$