A circular loop of radius \( r \) is carrying current \( 1 \, \text{A} \). The ratio of magnetic field at the centre of circular loop and at a distance \( r \) from the center of the loop on its axis is:
\( 1 : 3\sqrt{2} \)
\( 1 : \sqrt{2} \)
\( 3\sqrt{2} : 2 \)
\( 2\sqrt{2} : 1 \)