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

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

On Wed, Nov 10, 2021 at 10:13 AM Antti Savinainen via Phys-l <> wrote:


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

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)

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

Forum for Physics Educators