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

$1.0×10^{15}$

Number density of atom in silicon specimen = $5×10^{28}atoms\,m^{-3}= 5×10^{22}atoms\,cm^{-3}$. Since 1 atom of indium is doped $5×10^7$ in silicon atoms, so total number of indium atoms doped per $cm^3$ of silicon will be

$n=\frac{5×10^{22}}{5×10^7}=1.0×10^{15}$