The IR detector card, like the fluorescent and phosphorescent materials, consists of solids with impurity atoms. An energy band model can explain the observed properties of the card. Try to develop an energy band diagram the could explain the properties of the IR detector card.
Sketch your prediction and identify the energy bands of the materials and the energy or energies absorbed by the card (along with their sources) as well as the energy emitted by the card.
In the next activity, you will use a computer program to construct a model that explains the operation of the IR detector card.