Pupils discuss the principles of atomic structure that underlie the operation of a photovoltaic cell and explains how they apply to a photovoltaic cell's operation. An area of the classroom is staked off to represent a photovoltaic cell, and students form two groups. One group represents electrons lined up on the p-side of the p-n junction, waiting to receive energy from the photon to cross into the n-side and then proceed through the circuit.