A semiconductor has equal electron and hole concentration of `6 xx 10^8` per `m^3`. On doping with certain impurity, electron concentration increases to `9 xx 10^12` per `m^3` .The new hole concentration is

Explanation

`n_(i)=6xx10^(8)//m^(3) andn_(e)=9xx10^(12)//m^(3)`
(i) `n_(e) gt n_(1)` so it is N-type semiconductor
(ii) `because n_(i)^(2) =n_(e)n_(h) " "n_(h)=(n_(i)^(2))/(n_(e))=(36xx10^(16))/(9xx10^(12))=4xx10^(4)//m^(3)`