# If 'a' stands for the edge length of the cubic systems : simple cubic, body centred cubic and face centred cubic, then the ratio of radii of the spheres in these systems will be respectively

$\begin {array} {1 1} (1)\;1a : \sqrt 3 a : \sqrt 2 a & \quad (2)\;\large\frac{1}{2}a : \large\frac{\sqrt 3}{4}a : \large\frac{1}{2\sqrt 2}a \\ (3)\;\large\frac{1}{2}a : \sqrt 3 a : \large\frac{1}{\sqrt 2 }a & \quad (4)\;\large\frac{1}{2}a : \large\frac{\sqrt 3}{2}a : \large\frac{\sqrt 2}{2}a \end {array}$