A) \[\frac{4}{\sqrt{3}}r\]
B) \[\frac{4}{\sqrt{2}}r\]
C) \[2r\]
D) \[\frac{\sqrt{3}}{2}r\]
Correct Answer: B
Solution :
In face centred cubic unit cell the spheres occupy all the eight comers of the cube and also the centre of the six faces of the cube. A sphere at the centre of the face is shared by two unit cells and therefore makes a contribution of only 1/2 to a particular unit cell. The radius of the atom\[(r)=\frac{a}{2\sqrt{2}}\] a (edge length) \[=2\sqrt{2}r\] \[r=\frac{2\sqrt{2}r\times \sqrt{2}}{\sqrt{2}}\] \[=\frac{4r}{\sqrt{2}}\]
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