While the discharge of an electroscope is a neat demo the students haven't been presented with any electrostatics or electrodynamics yet. Also the students have not constructed a relationship between color and frequency yet (could be wavelength too). Students haven't constructed the relationship between potential (voltage) and energy nor have they determined the charge of an electron. Additionally due to the cost of the photo-electric experiment equipment it is doubtful that there would be enough for multiple groups of students to perform the experiment. The simulation that the materials suggest plot all of the data automatically for the students and one of the graphs uses E instead of V in the plot versus frequency.
I believe that the photon model should be included after the Bohr model. However if I do include it in the light unit as a capstone class lab I think I could be successful in a modeling approach if Vcutoff vs. Intensity and Vcutoff vs. frequency can be plotted. The following is how I would do it:
1. Present a solar cell powered toy, calculator, etc. and ask students what is happening here in terms of energy (encourage energy pie charts). Students might mislabel the energy storage mechanism for light don't worry about this but hopefully they would say something like Elight which is later stored as Eelect, Ek and Edis.
2. If students haven't already developed the idea that the energy of a wave is related to it amplitude this should be done now (multiple speakers quiet in and of themselves sound loud together--thus lots of energy--which can be shown to have larger amplitude on an oscilloscope, swinging pendulum shows that larger amplitude has more energy). Additionally students need to see that brighter sources have more energy and are said to be of greater intensity (show bathroom light bar with one light, two, etc. all of equal bright intensity but together greater intensity = more energy).
3. Students need to accept that this new term Voltage is related to energy. This could be done by having students note the effects of increased voltage on a light bulb (greater voltage = greater brightness and thus more energy).
4. Ask students to predict which characteristics of a wave might effect the voltage (Eelect) of the circuit. Anticipated answers Intensity, wavelength, and frequency. Help students to see that since wavelength and frequency are related to the speed of light which is a constant then we only need to test one of these. Further help them see that the different light sources are different colors and remind them of the connection between color and frequency. Recommend that students plot Vcutoff vs. frequency first.
5. The mathematical model found from Vcutoff vs. frequency indicates that the wave model is justified.
6. Have students come back and whiteboard their preliminary results indicating the wave nature of light and then ask them to predict the relationship they will get for Vcutoff vs. Intensity for a particular frequency of light that gives a non-zero voltage. This prediction should be direct.
7. Now have students go back into lab and have them plot Vcutoff vs. intensity.
8. Have students come back and whiteboard their results (no relationship) and ask them what this implies about the wave-model of light. Ask them to suggest another model for light and hopefully they will suggest the particle model again.
9. Given that only one particle of light can interact at a time what does it mean to have a more or less intense light source. They should suggest more particles per second (not faster just more). If they are having trouble with this have the students sketch the photo-electric effect equipment set-up and have them sketch in particles coming from the light. Now ask them to predict what the Vcutoff vs. intensity graph would look like again given that only one particle can interact at a given time. Hopefully they will suggest a digital square-wave looking graph with the maximum being a cutoff. Each square represents a particle of light's amount of energy being stored as Eelect then it would drop back to zero. As the intensity increases the density of these squares would increase maintaining a constant Vcutoff.
10. Recap for student what the graph Vcutoff vs. f suggests about the nature of light and what Vcutoff vs. Intensity suggests about the nature of light. In other words when light interacts with matter we need to use the particle model of light we call these particles photons and otherwise we need to use the wave model of light. This is known as the photon model of light which we need to use from now on.