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[Phys-L] Photoelectric effect: electron current vs. frequency


I am currently teaching a HS course on modern physics. I have taught it for many years by using a Phet simulation, which is free and pretty versatile:

One question type in exams is to ask what kind of plot correctly depicts the relationship between the electron current and frequency of light, assuming that the frequency is above the critical frequency for a given metal. The standard answer is that the current is constant w.r.t. frequency. For instance, the Khan Academy ( explains it thusly:

"Because the light amplitude was kept constant as the light frequency increased, the/number/of photons being absorbed by the metal remained constant. Thus, the rate at which electrons were ejected from the metal (or the electric current) remained constant as well. The relationship between electron current and light frequency is illustrated in graph (b) above."

However, when the situation is run using the Phet simulation, the current doesn't stay constant: it increases when the frequency of light increases (that is, the wavelength decreases).

Which one is correct?

Best wishes,

Antti Savinainen, PhD

Kuopio Lyseo HS, Finland