Consider two uniform discs of the same thickness and different radii $R _ { 1 } = R$ and $R _ { 2 } = \alpha R$ made of the same material. If the ratio of their moments of inertia $I _ { 1 }$ and $I _ { 2 }$, respectively, about their axes is $I _ { 1 } : I _ { 2 } = 1 : 16$ then the value of $\alpha$ is:\\
(1) $2 \sqrt { 2 }$\\
(2) $\sqrt { 2 }$\\
(3) 2\\
(4) 4