If $NaCl$ is doped with $10^{-3} \ mol \ \%$ $SrCl_2$,then the concentration of cation vacancies will be

Analysis of the density of an electrically neutral $NaCl$ crystal containing vacancies yielded the following results:
$(i)$ Density of $NaCl$ crystal with all sites occupied $= 2.178 \times 10^3 \ kg \ m^{-3}$
$(ii)$ Density of $NaCl$ crystal with vacancies $= 2.165 \times 10^3 \ kg \ m^{-3}$
Then the percentage of vacancies in the $NaCl$ crystal is .....

$A$ silicon specimen is made into a $p-$type semiconductor by doping,on an average,one indium atom per $5 \times 10^7$ silicon atoms. If the number density of atoms in the silicon specimen is $5 \times 10^{28} \ \text{atoms} \ m^{-3}$,then the number of acceptor atoms in silicon per cubic centimeter will be

Assertion : Due to Frenkel defect,there is no effect on the density of the crystalline solid.
Reason : In Frenkel defect,no cation or anion leaves the crystal.

Schottky defect in a crystal arises due to

What is a point defect?