If $ \overline B$ is the magnetic induction, at the centre of a circular coil of radius 'r' carrying a current is 1 T then its value at a distance of $ \sqrt 3 \: r$ on the axis from the centre of the coil is:

Question

$\begin {array} {1 1} (1)\;\large\frac{1}{8}T & \quad (2)\;\large\frac{1}{16}T \\ (3)\;8\: T & \quad (4)\;\large\frac{1}{4}T \end {array}$