A charged particle P leaves the origin with speed v = v₀ at some inclination with the x-axis. There is a uniform magnetic field B along the x-axis. P strikes a fixed target T on the x-axis for a minimum value of B = B₀. P will also strike T if

Let d = distance of the target T from the point of projection. P will strike T if d is an integral multiple of the pitch.

$\text{ Pitch }=\left(\frac{2\mathrm{\pi m}}{\mathrm{QB}}\right)\mathrm{vcos}\mathrm{\theta }=\mathrm{k}\left(\frac{\mathrm{v}}{\mathrm{B}}\right)$

where k = constant

Initially. pitch: $\mathrm{d}=\mathrm{k}\left(\frac{{\mathrm{v}}_0}{{\mathrm{B}}_0}\right)$

For the given options if pitch ${\mathrm{d}}^{\mathrm{\prime }}=\frac{\mathrm{d}}{2},\frac{\mathrm{d}}{3},\frac{\mathrm{d}}{4},\dots ,$ etc., then charge will hit the target.