JEE PYQ: Solid State Question 23
Question 23 - 2019 (11 Jan Shift 2)
The radius of the largest sphere which fits properly at the centre of the edge of a body centred cubic unit cell is:
(Edge length is represented by ‘$a$’)
(1) 0.027 a
(2) 0.047 a
(3) 0.134 a
(4) 0.067 a
Show Answer
Answer: (4)
Solution
For BCC, $R = \dfrac{\sqrt{3},a}{4}$. Empty space at edge $= a - 2R = a - \dfrac{\sqrt{3},a}{2}$ = diameter of sphere. $r_{\text{sphere}} = \dfrac{a - \dfrac{\sqrt{3},a}{2}}{2} = \left(\dfrac{2 - \sqrt{3}}{4}\right)a = 0.067,a$.
BETA
