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 that is used to coat the insides of the fluorescent lamps.
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 Mercury gas in the diagram above begins to glow with a color corresponding to the input spectrum energy. 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, and then from the impurity state to the ground state. The energy corresponding to this last transition appears on the Output spectrum below the energy level diagram and the lamp on the left of the screen begins to glow with that color. The material of the coating in the cross sectional view below the lamp also begins to glow.
Click the "Edit Properties" button, and observe then click and drag the energy bands on the energy level diagram. After adjusting the bands to a new value, you may need to alter the input energy on the slider so that the input energy is greater than the excited state band energy. Then click the "Turn on Lamp" button to repeat the transitions.Direct comments to: Chandima Cumaranatunge (programming aspects); Sanjay Rebello (physics content).