$\mathrm{B}_{1}=\frac{\mu_{0} \mathrm{i}}{4 \pi\left(\frac{\mathrm{L}}{2}\right)}(\sin \alpha+\sin \beta)$
or $\quad \mathrm{B}_{1}=\frac{\mu_{0} \mathrm{i}}{2 \pi \mathrm{L}}\left(\sin 45^{\circ}+\sin 45^{\circ}\right)=\frac{\mu_{0} \mathrm{i}}{\sqrt{2} \pi \mathrm{L}}$

Reason : Any two charged particles having equal kinetic energies and entering a region of uniform magnetic field $\overrightarrow B $ in a direction perpendicular to $\overrightarrow B $, will describe circular trajectories of equal radii.
