Question

A neutron, a proton, an electron and an $\alpha$-particle enter a region of uniform magnetic field with the same velocities. The magnetic field is perpendicular and directed into the plane of the paper. The tracks of the particles are labelled in the figure. The electron follows the track

• A. A
• B. B
• C. C
• D. D

Answer 1

Answer: (D)

Radius of path, $r=\frac{mv}{qB}$
If $\left(\frac{m}{q}\right)$ is least, $r$ will be least
$\because \left(\frac{m}{q}\right)$ is least for an electron so the path of electron will be track $D$.