Answer:
Explanation: Sure, I can help you with that. The intrinsic Fermi energy is given by the equation: Ei = (Nc + Nv)/(2 * Nc * Nv) * E, where E is the midgap energy. Plugging in the values we have, we get:
Ei = (3.28e19 + 1.47e19)/(2 * 3.28e19 * 1.47e19) * (-73/2) = -0.31 eV
At 27°C, we have: Ei = (3.28e19 + 1.47e19)/(2 * 3.28e19 * 1.47e19) * (27/2) = 0.31 eV
And so on for other temperatures. As for your second question, it is not reasonable to approximate Ei as simply the midgap energy for all of these temperatures, as the effective densities of states change with temperature. However, at low temperatures like -73°C and 127°C, the approximation may be more accurate. At 27°C, the difference between Ei and the midgap energy is about 0.03 eV, which is relatively small compared to the total energy range of silicon.