 | TEACHERSí NOTES FOR THE PHOTOELECTRIC EFFECT VIRTUAL LAB |
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PHYSICS APPROXIMATIONS
Some comments regarding the level of realism associated with this virtual lab are in order.
VARIABILITY IN THE DATA
There is variability built into the data generation. It is generally on the order of 10-20% variability. Therefore, two students who run the same test and generate a single data point each may be in significant disagreement with one another. This is a real situation in science and, indeed, is one of the reasons why physicists strive for lots of data ó making measurements of things like photons and electrons can be tricky business! The level of variability in real-world labs would, of course, vary dependent upon the expertise of the scientist and the type of equipment being used. The variability implemented here is great enough to encourage the gathering of lots of data, but not so great that it obscures the physical effects.
NUMBER OF ELECTRONS??
Any graph, in this virtual lab, that displays the "number of electrons" is a graph that is indulging in a bit of fiction. Since the number of liberated electrons is dependent upon the time duration and the absolute intensity of the light, the data for those graphs is fallacious in any number of ways. On the other hand, the shape of those graphs is completely consistent with the physics of the photoelectric effect and many important, qualitative, observations can be made based upon those graphs. One can always assume an arbitrary time frame and an arbitrary, absolute, intensity that will make these graphs quantitatively correct, but it is hardly necessary to do so since the lessons of the photoelectric effect can be learned without such assumptions. It is important to recognize that one CANNOT, from this virtual lab alone, predict the actual number of electrons that would be produced in a real-world photoelectric lab.