An electron in the ground state of hydrogen atom is revolving in anti-clockwise direction in the circular orbit of radius R as shown in figure.

The atom is placed in a uniform magnetic induction B such that the plane normal of the electron orbit makes an angle `30^(@)` with the magnetic induction. Find the torque experienced by the orbiting electron.

Explanation

Torque on the orbiting electron in uniform magnetic fields is
`vec( tau) = vec( M ) xx vec( B )`
or `tau = MB sin 30^(@)`
or ` tau = ( eh)/( 4 pi m ) xx( B)/( 2) = ( ehB)/( 8 pi m )`