Question

A neutron, a proton, an electron and an alpha particle enter a region of constant magnetic field with equal velocities. The magnetic field is along the inward normal to the plane of paper. The tracks of the particles are labeled in Fig. Which of the tracks show the path of the electron and α-particle?

Answer 1

Since neutron is a neutral particle hence it does not experience any force in \(\vec B\). Hence its track is given by path C.

Applying Fleming’s left hand rule, we find that the electron will be deflected towards right. Hence the track D represents the path of electron. And proton and α-particles are deflected towards left.

Since radius of a charged particle in magnetic field B is given by

i.e. the track of α-particle is less curved than that of proton.

Hence, the track A is the path of proton and track B represents the path of α-particle.