CBSE 2025 · Region 6 · Set 1 · Q6 · 1 mark

A proton and an $\displaystyle \alpha$-particle enter with the same velocity $\displaystyle \overrightarrow{\mathrm{v}}$ in a uniform magnetic field $\displaystyle \vec{B}$ such that $\displaystyle \vec{\mathrm{v}} \perp \vec{B}$. The ratio of the radii of their paths is :

CBSE Class 12 Physics past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.