The density of an electron - hole pair in a pure germanium is `3xx10^(-16) m^(-3)` at room temperature. On doping with aluminium , the hole density increase to `4.5xx10^(22) m^(-3)` Now the electron density ( in m ) in doped germanium will be

Options

A. `1xx10^(10)`
B. `2xx10^(10)`
C. `0.5xx10^(10)`
D. `4xx10^(10)`

Answer

B

Explanation

`n_(i)^(2)=n_(h)n_(e)rArrn_(e)=((3xx10^(16))^(2))/(4.5xx10^(22))=(9xx10^(12))/(4.5xx10^(22))=2xx10^(10)m^(-3)`