An electron in the ground state of a hydrogen atom is revolving in an anticlockwise direction in a circular orbit of radius $r$. The atom is placed in a uniform magnetic field $B$ in such a way that the magnetic moment of the orbital electron makes an angle of $30^{\circ}$ with the magnetic field. The torque experienced by the orbital electron is

  • A
    $\frac{ehB}{4\pi m}$
  • B
    $\frac{ehB}{8\pi m}$
  • C
    $\frac{ehB}{2\pi m}$
  • D
    $\frac{\sqrt{3}ehB}{8\pi m}$

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