GATE EC 2004 Set 1 Q39 — Electronic Devices

The resistivity of a uniformloy doped $n$-type silicon sample is $0.5 \; \Omega-\mathrm{cm}$. If the electron mobility $\left(\mu_{n}\right)$ is $1250 \mathrm{~cm}^{2} / \mathrm{V}$-sec and the charge of an electron is $1.6 \times 10^{-19}$ Coulomb, the donor impurity concentration $\left(\mathrm{N}_{\text{n}}\right)$ in the sample is