This interactive simulation provides a basic design for a discharge lamp and explain the function of the different components. It helps the user understand the basic structure of an atom and relate it to the color of light produced by discharge lamps. The user can set the voltage of the electrodes in a simulated discharge tube and  view the energy level transitions and spectra of the atoms excited by the electrons in the tube. The user can use one of the typical lamps (hydrogen, mercury, sodium, neon) or design their own.

This simulation is part of a large and growing collection. It has been designed using principles from physics education research and refined based on student interviews.