An electron and a proton enter a region of uniform magnetic field, in a direction at right angles to the field, with the same kinetic energy. They describe a circular paths of radius $r_{\mathit{e}}$ and $r_{\mathit{p}}$, respectively. Then,

A particle with charge $q$, moving with a momentum $p$ enters a uniform magnetic field normally. The magnetic field has magnitude $B$ and is confined to a region of width $d$, where $d<\frac{p}{Bq},$ The particle is deflected by an angle $\theta$ in crossing the field

To which of the following quantities, the radius of the circular path of a charged particle moving at right angles to a uniform magnetic field is directly proportional?

A cyclotron is used to accelerate protons $\left({}_1{}^1\mathrm{H}\right)$, Deuterons $\left({}_1{}^2\mathrm{H}\right)$ and $\alpha$- particles $\left({}_2{}^4\mathrm{He}\right)$. While exiting under similar conditions, the minimum K.E. is gained by