UTF-8Atoms can store energy by going into excited states255255204
The atom in the model below has two excited states above the ground state. It can make transitions between any pair of states, either emitting or absorbing a photon when it does so. The excited states are unstable meaning that the atom will only stay in them a short time before decaying to a lower state. (In the model we have slowed down this process tremendously. In reality the atom only stays in the excited state for a tiny fraction of a second.)
You can put the atom into an excited state by [How? We need a way to do this. It would be good if the energy level diagram could double as a controller of the model -- that way we could show the atom on the energy level diagram and move it from one level to another. Also, it would be very useful if we could "lock" the energy level diagram so that the kids couldn't change it. Then we can unlock it later on, when we want them to experiment with different energy levels.] Watch carefully and see if you can identify which photons correspond to which transitions.
Here I want to put a question in which the student is presented with a series of snapshots of an atom and a photon that it has just emitted, and is asked to draw an arrow between the initial and final states of the transition that created that photon. I don't know how to do that, though, because the snapshot facility only works with the model.
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<b><font size="5" face="Trebuchet MS">Atoms have many excited states</font></b>
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