For an extrinsic semiconductor, mark the donor and acceptor levels on an energy-band diagram.

Explain that the energy of a hole deep in the valence band is high.

Draw separate energy-level bands for conductors, semiconductors and insulators and label each of them to illustrate the behaviour of a conductor.

Draw a labelled energy band diagram for a solid which is an insulator. What is the main difference between this diagram and that of a semiconductor?