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Q)

In pure semiconductor number of conducting electrons is $5 \times 10^{20}$ per cubic meter. How many holes are there in $1 cm^3$ of the same semiconductor.

$(a)\;5 \times 10^{14} \\ (b)\;5 \times 10^{-14} \\ (c)\;10^{-10} \\ (d)\;5 \times 10^{20}$

$\qquad= (volume \;of \;given \;sample) \times 5 \times 10^{20}$
$\qquad= 10^{-6} \times 5 \times 10^{20}$
$\qquad= 5 \times 10^{14}$