NEET Physics Semiconducting Devices NEET PYQ-Semiconducting Devices

If the lattice parameter for a crystalline structure is \[3.6\,\,\overset{o}{\mathop{A}}\,,\] then the atomic radius in fee crystal is                                                                                                            [AIPMPT (S) 2008]

A) \[1.81\,\overset{o}{\mathop{A}}\,\]

B)                  \[2.10\,\overset{o}{\mathop{A}}\,\]

C) \[2.92\,\overset{o}{\mathop{A}}\,\]

D)      \[1.27\,\overset{o}{\mathop{A}}\,\]

Correct Answer: D

Solution :

Atomic radius is the distance between two nearest neighbours. For fee crystal

Atomic radius \[=\frac{1}{2\sqrt{2}}\times \] lattice parameter

or \[r=\frac{a}{2\sqrt{2}}\]

or \[r=\frac{3.6}{2\sqrt{2}}{\AA}=1.27{\AA}\]