The ratio of the radius of gyration of a thin uniform disc about an axis passing through its centre and normal to its plane to the radius of gyration of the disc about its diameter is :
(1) 4 : 1
(2) 1 : $\sqrt2$
(3) 2 : 1
(4) $\sqrt2$ : 1
(1) 4 : 1
(2) 1 : $\sqrt2$
(3) 2 : 1
(4) $\sqrt2$ : 1