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:

Emission lines in atoms are generated whenever electrons move from a higher energy level to a lower energy level. One photon is given off per transition and the energy of that photon is exactly the same as the energy level difference.

Atoms are governed by rules called transition probabilities and they dictate the most probable way in which an electron moves from higher to lower energy levels.

In this small applet, students can interact with a virtual atom to observe the photons emitted as an electron cascades down energy levels.

Suggested Activities:

• Student can click on the electron and position it in some energy level.

• Students can then record the wavelengths of the emitted photons and hence observe the emission line spectrum of the atom. Via parameter tags, any kind of atom (real or fake) can be set up.

• Try setting up atoms with essentially forbidden transitions (very low probability) to see if the students get the fact that certain wavelengths which could be there, are generally not observed.