Click on the "Create Excited State Band" button to the right of the energy level diagram. An excited state band appears. Then click the "Create Impurity State Band" button below, and an impurity state band appears below the excited state band.
Drag the "Input Energy" slider at the bottom left of the screen to increase the input energy of the First Source to the infrared detector. Observe the marker on the vertical scale of the energy level diagram rise to indicate the increase in the impute energy. When the input energy is greater than the energy of the excited state band. Click the "Turn on Lamp" button. The First Source lamp begins to glow with a color corresponding to the input spectrum and the infrared detector card is illuminated. On the energy level diagram observe a transition from the ground state to the excited state and then another from the excited to the impurity state. The shades of the energy bands reflects their population. Finally, the electrons are in the impurity state.
The card that was illuminated with the First (visible) source appears at the top left of the screen in front of the Second (infrared) source. Increase the energy of the infrared source using the slider. Observe the marker on the vertical scale of the energy level diagram rise to indicate the increase in the input energy. Increase the energy until the marker is past the excited state band. Then click the "Turn on Lamp" button. Observe the transition from the populated impurity state to the excited state and then down to the ground state. The spectral line of the transition from the excited to the ground state appears in the diagram below and the card begins to glow with the corresponding color.
Click the "Replay" button and observe the sequence of illuminations by the two light sources and the resulting transitions repeat.Direct comments to: Chandima Cumaranatunge (programming aspects); Sanjay Rebello (physics content).