We have this basic PASCO Photoelectric Effect equipment in our lab and there are two things I would like to ask about the experiment.

  1. We keep either the area apertures or wavelength filters fixed and change the other one to collect data. In both cases, the current vs. voltage graph is exponentially increasing. What is the reason for that exponential increase? I couldn't find any source/manual explaining the photodiode in detail but it seems like this behavior is related to the photodiode, specifically to a charging capacitor. Can anybody give more details about that (explain this behavior) or maybe attach a link about the photodiode?
  2. In the theory part of the experiment, we say that according to the classical wave theory we expect a change in the stopping potential when the intensity is changed. But, photon theory predicts no change in the stopping potential. In the experiment, we change area apertures to change the intensity of light, i.e. we choose a bigger area, place it into the entrance slit of the photocell and we say that intensity of light is increased. But, this is only true if we describe intensity as "photon flux" since in this case only number of photons striking on cathode is changing. However, if we define intensity as power "per unit area" as in the classical theory then increasing the area aperture doesn't change the intensity (if I'm not wrong). So, my question is: are these two definitions of intensity related? If so, how? And from the perspective of classical theory, can we say that changing the area apertures also changes the intensity?

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