Observe the absorption spectrum of an LED by dragging any of the LEDs from the bottom left of the screen and dropping it into the LED Socket above. The spectrum appears at the top right of the screen.
Click on the "Add Conduction Band" button. A conduction band will appear on the scale. Then click on the "Add Valence Band" button just below it and a valence band will appear below the conduction band on the scale. A thick arrow representing the transition from the conduction to the valence band will appear on the energy diagram. Simultaneously, the trial spectrum corresponding to this transition will appear directly below the real spectrum of the LED.
Move the cursor to the center of either band. The cursor changes to a hand. Drag the energy band up or down and see the spectrum change. Change the width of the energy band and the resulting spectrum by moving the cursor close to the top or bottom edge of either band and adjusting the edge of either band.Direct comments to: Chandima Cumaranatunge (programming aspects); Sanjay Rebello (physics content).