The Atom and the Quantum

Go to the PhET website at: http://phet.colorado.edu. Click "Play with Sims"; then

"Physics", and then "Quantum Phenomena" on the left-hand side menu. Find and run (or download to the desktop) the simulation "Models of the Hydrogen Atom".

Move the switch onto Prediction:

Select the Atomic Model: Bohr

Check the box Show electron energy level diagram

Now adjust the Light Controls as shown. You are now bombarding the atom with high-frequency photons of the wavelength of 95 nm (nanometers.)

The hydrogen atom is in its ground state, with electron remaining in the lowest energy level n =1. Watch what happens when the atom absorbs a single photon.

1. To what energy level does the electron jump? (Watch the number in the lower right corner and the energy level diagram).

2. How does the electron return to the ground state? In one jump, or in few smaller jumps? (Watch the number in the lower right corner and the energy level diagram).

When the electron jumps down, the atom emits a single photon of a specific wavelength, represented by a dot on the spectrum. Check the box "Show spectrometer".

3. How many spectral lines should result considering all possible transitions?

4. How many lines are actually seen in the spectrometer?

5. How many of these are visible to a human eye?

Select the Atomic Model: de Broglie

6. Describe how excited state of the atom is now represented.

7. Does the de Broglie model give you different set of spectral lines?

Select the Atomic Model: Schrödinger. Note that that sooner or later (usually very soon) no more photons are emitted and a warning "Excite Atom" appears. Click on it to resume action.

8. Describe how excited state of the atom is now represented.

9. Does the Schrodinger model give you different set of spectral lines? What's the difference?

Now move the switch onto Experiment.

10. Which model best fits the experiment?