An alpha particle (mass \(6.4 \times 10^{-27} \text{ kg}\) and charge \(3.2 \times 10^{-19} \text{ C}\)) having \(8.0 \text{ MeV}\) energy, enters a region of a uniform magnetic field of \(0.5 \text{ T}\). If the field is directed perpendicular to the velocity of the particle, find the radius of the circular path described by the particle. Mention the condition under which the particle in this region (i) describes a helical path, and (ii) goes straight undeviated.
