Assuming dopant atoms are uniformly distributed in a silicon crystal, how far apart are these atoms when the doping concentration is a) 10l5 cm-3, b) 1018 cm-3, c) 5times1020 cm-3. Estimate the resistivity of pure silicon in Ohm-cm at a) room temperature, b) 77K. and c) 1000 degree C. You may neglect the temperature dependence of the carrier mobility in making this estimate.