A neutron , an electron and an alpha particle moving with equal velocities, enter a uniform magnetic field going into the plane of the paper as shown in fig. Trace their paths in the field and justify your answer.

Explanation

The paths of an `alpha-` particle, neutron and an electron moving with equal velocities, in a uniform magnetic field `vecB` going into the plane of the paper have been depicted in the fig.
(i) The positively charged alpha- particle describes a circular path of radius `r_(alpha)` in hte plain of paper in an anticlockwise direction under the magnetic force where `r_(alpha) = (m_(alpha) v)/(q_(alpha) B)`.
(ii) The neutron, being a chargeless particle, experience no force due to magnetic field and travels with a constant velocity along a straight path.
(iii) The negatively charged electron describes a circular path of radius, `r_(e) = (m_e v)/(eB)` in the clockwise diretions under the magnetic force. As `m_e < < m_(alpha) `, hence `r_(e) < < r_(alpha)`.