Two charged particles M and N enter a region of uniform magnetic field with velocities perpendicular to the field. The paths of particles are shown in Fig. The possible reason is

The radius of the circular path of a particle of mass m, charge e moving with a speed v perpendicular to a magnetic field B is given by

$\frac{m{v}^2}{r}=evB\text{ or }r=\left(\frac{m}{e}\right)\frac{v}{B}$

Thus, r is inversely proportional to $\left(\frac{e}{m}\right)$, the charge to mass ratio.

As we can see M is having smaller radius of curvature than N, So the charge to mass ratio M is greater than that of N.