What do you understand by $p$- and $n$-type semiconductors? Distinguish between them on the basis of energy band diagram.

Distinguish between intrinsic and extrinsic semiconductors.

Explain briefly what is meant by extrinsic semiconductors, including the terms donor and acceptor impurities as well as $p$-type and $n$-type semiconductors.

Using the concept of electron and hole currents, derive expression for the conductivity of a semiconductor.

What do you understand by band theory of energy in solids? Define valence band, conduction band and forbidden gap.

What is doping in semiconductors? Explain $p$ and $n$-type of semiconductors by selecting an element from third and fifth group and also explain acceptor and donor nature of these elements mixed with a pure semiconductor.