Answer
(c) reduced, reversed
Work Step by Step
We know that a charged particle moves in a circular path, if the velocity (v⃗ ) of the particle is perpendicular to a uniform magnetic field (B⃗ ). In that case, the radius (r) of the circle is given by the formula: $r=\frac{mv}{|q|B}$, where m is the mass of the particle and q is the charge of the particle. In our case the velocity remains constant. As the electron is negatively charged (opposite to the charge of a proton) the magnetic field has to be reversed so that the direction of force remains same. As the mass of electron is less than proton, the magnitude of the magnetic field has to be reduced so that the radius of the circular path remains same and the electron follows exactly the same path as the proton.
