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. The are the bands in the material of toothbrush.
Drag the "Input Energy" slider at the bottom left of the screen to increase the input energy of the First Source. Observe the marker on the vertical scale of the energy level diagram rise to indicate the increase in the input 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 toothbrush 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, toothbrush is next immersed in a beaker of liquid nitrogen, and electrons remain in the impurity state.
The toothbrush that was illuminated with the First source appears at the top left of the screen in front of the Second source which is heat lamp. Increase the temperature of the heat lamp 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 toothbrush 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.
Click and vertically drag the excited and impurity state bands. Then repeat STEPs 2 and 3, to obtain a new Output spectrum corresponding to these bands.