Q 12-04-146JEE MainJEE Main 2022 (26 Jun, Shift 1)Easy
A proton and an alpha particle of the same velocity enter a uniform magnetic field which is acting perpendicular to their direction of motion. The ratio of the radii of the circular paths described by the alpha particle and proton is
Answer: (B) $2 : 1$
$r = \dfrac{mv}{qB}\propto\dfrac mq$ for equal $v$:
$$\frac{r_\alpha}{r_p} = \frac{4m/2e}{m/e} = 2$$
Solution by Sreeraj P, M.Sc Physics