The packing factor is calculated as:
\[\text{Packing Factor} = \frac{\text{Volume of atoms in a unit cell}}{\text{Volume of the unit cell}}\]
For FCC, the packing factor is:
\[\text{Packing Factor} = \frac{4 \times \frac{4}{3} \pi r^3}{a^3} = 0.74\]
where \(a = \frac{4r}{\sqrt{2}}\). This indicates that \(74\%\) of the unit cell volume is occupied by atoms.
Match Fibre with Application.\[\begin{array}{|l|l|} \hline \textbf{LIST I} & \textbf{LIST II} \\ \textbf{Fibre} & \textbf{Application} \\ \hline \hline \text{A. Silk fibre} & \text{I. Fire retardant} \\ \hline \text{B. Wool fibre} & \text{II. Directional lustre} \\ \hline \text{C. Nomex fibre} & \text{III. Bulletproof} \\ \hline \text{D. Kevlar fibre} & \text{IV. Thermal insulation} \\ \hline \end{array}\]