Two windows should be open. This one in which the instructions are given and a smaller one which contains the actual applet that we will be using.

Tutorial:

In this case we have a hot source, whose temperature can be controlled. This is a source of incoming photons that may or may not ionize the gas. A recombination line spectrum is shown.

The total number of photons emitted is counted and the number of ionizing events is counted. The student should adjust the temperature to see how this balance is effected. The recombination line spectrum can be measured with the mouse. Mousing over a line will show the wavelength and intensity.

The atom set up here is an idealized atom but the same parameter tag field described in the Atomic Emission applet applies here and so one can also make real atoms.