The magnetic field due to a small magnetic dipole of magnetic moment $M$,at a distance $r$ from the centre on the equatorial line is given by (in $M.K.S.$ system):

• A
  $\frac{\mu_0}{4\pi} \times \frac{M}{r^2}$
• B
  $\frac{\mu_0}{4\pi} \times \frac{M}{r^3}$
• C
  $\frac{\mu_0}{4\pi} \times \frac{2M}{r^2}$
• D
  $\frac{\mu_0}{4\pi} \times \frac{2M}{r^3}$