Physics 9702 · AS & A Level · Energy levels in atoms and line spectra

Energy levels in atoms and line spectra — practice question

Some of the electron energy bands in a solid are shown in Fig. 12.1.
(a)[3]

In isolated atoms, electron energy levels have discrete values. Suggest why, in a solid, energy bands form instead of discrete energy levels.

(b)[5]

A light-dependent resistor (LDR) consists of an intrinsic semiconductor. Use band theory to explain how the resistance of the LDR depends on light intensity when the temperature is constant.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Electrons in neighbouring atoms are sufficiently close to interact” …

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