Which one of the following statements is not correct?

Options

A. Schottky defect in ionic solids does not change the density of the crystal
B. Packing efficiency is the percentage of total space filled by the particles
C. In body centered cubic unit cell, the relationship between atomic radius (r ) and the edge length (a) is , r = `(sqrt(13))/(4)` a
D. Photovoltaic cell is used for conversion of light energy into electrical energy

Answer

A

Explanation

Schottky defect is type of point defect in a crystal lattice in which ions leaves their lattice sites leaving vacancy. Hence, it decreases the density of crystal.
(b) Packing efficiency is percentage value of total space filled by the particles.
packing efficiency
`= ("Volume of atom occupied")/("Total volume of unit cell") xx 100 `
In bcc crystal lattice
R + 2R + R = `sqrt(3a)`
4R = `sqrt(3)` a
`R = (sqrt(3))/(4) a`
Photovoltaic cell is used for conversion of light energy into electrical energy,
Hence, option (a) is incorrect.