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

[Philip Keller <pkeller@holmdelschools.org>]

Very much not an expert, but:  if the frequency is higher the
photoelectrons come out with higher speed. Then,as long as the  voltage is
below the stopping potential, wouldn't a larger number of the electrons
happen to be moving in a direction that lets them make it across the gap to
the other electrode?  So though there are not more electrons being
liberated, we do see a higher current?  Prepared to be quite mistaken
here...

On Wed, Nov 10, 2021 at 10:13 AM Antti Savinainen via Phys-l <
phys-l@mail.phys-l.org> wrote:

> Hi,
>
> 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:
>
> https://phet.colorado.edu/en/simulations/photoelectric
>
> 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
> (
> https://www.khanacademy.org/science/physics/quantum-physics/photons/a/photoelectric-effect)
>
> 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
>
>
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