Q: Fraction of total volume occupied by atoms in a simple cubic cell is
(A) π/2
(B) √3π/2
(C) √2π/2
(D) π/6
Ans: (D)
Sol: In simple cubic arrangement, no. of atoms = 1
a = 2r
Packing fraction = Volume occupied by one atom / Volume of unit cell
$\large = \frac{\frac{4}{3}\pi r^3}{a^3} $
$\large = \frac{\frac{4}{3}\pi r^3}{(2r)^3} = \frac{\pi}{6} $