Question

Protons and $\alpha$-particles of equal momenta enter a uniform magnetic field normally. The radii of their orbits will have the ratio

• A. 1
• B. 2
• C. 0.5
• D. 4

Answer 1

The correct option is B 2

$r=\frac{mv}{qB}$

$=\frac{p}{qB}\Rightarrow \frac{r_p}{r_{\alpha }}$

$=\frac{q_{\alpha }}{q_p}=\frac{2e}{e}=\frac{2}{1}$