The figure shows a long cylindrical straight wire of radius $a$ carrying steady current ($I$). The current ($I$) is uniformly distributed across the cross-section of the wire. The ratio of the magnetic fields at points $r =\frac{a}{3}$ and $r =\frac{a}{2}$ respectively is: Here $r$ is the distance of point from the axis of cylinder.

2 : 3

The correct answer is Option (1) → 2 : 3