Re: photoelectric effect (clarifications)

[Jack Uretsky <jlu@HEP.ANL.GOV>]

Dear Antti-
        The trouble with the fictitious history is that puts the
historical context of Einstein's work completely out of context and
trivializes the depths of Einstein's insight.  The fact is, to summarize
my comment, that there were no substantial "classical" predictions because
the notion of "electron" was foreign to 19th century physics.
        Consider. Hertz observed (~1885, I think) sparks emanating from
metal surfaces that were exposed to uv light while being subject to
strong electric fields.  It wasn't until 15 years later that JJ Thompson
determined that cathode rays had corpuscular constituents with an e/m
that we now ascribe to the electron.  It was not understood at that time
that a metal could be described as a sea of electrons.  And, most
importantly, it had not been determined, at the time of Einstein's paper,
that the maximum energy of a photoelectron was dependent on the frequency
of the incident light.  THAT WAS EINSTEIN'S PREDICTION, later borne out
by experiment.
        So Einstein's genius encompassed more than just the quantization
of light - it encompassed an insight into the nature of electrical
conduction in metals, the nature of the metallic state (including, I
believe, the concept of the "work function"), and a view of the
interaction of electromagnetic waves with charged corpuscles.
        There were no "erroneous 19th century explanations" because there
was not yet much of anything to explain.
        See "Introduction to Modern Physics" by Richtmeyer, Kennard, and
Lauritsen (McGraw-Hill), which provides citations to the original papers,
for a more detailed history.  I think you will do your students a favor if
you put Einstein's work in its correct historical context.

        I am, incidentally, looking forward to re-reading Einstein's
1905 paper.
                                Regards,
                                        Jack

Adam was by constitution and proclivity a scientist; I was the same, and
we loved to call ourselves by that great name...Our first memorable
scientific discovery was the law that water and like fluids run downhill,
not up.
                          Mark Twain, <Extract from Eve's Autobiography>

On Wed, 8 Nov 2000, Savinainen Antti wrote:

> Hi Jack (and others),
>
> > 2. Experiment shows that the maximum electron energy is
> > determined by the frequency, not the intensity, of the light.
>
> > The teacher discusses with the class some of the unsuccesful
> > calculations that were attempted in stage 2.
>
> > My question -for Savinainen only- is, is this roughly the
> > framework that led to your question?  If so, I can comment on your
> > question.
>
> that was exactly my motivation for the question. My IB students could be asked to explain the classical predictions of the photoelectric effect. I didn't like the contradiction which I found regarding the classical predictions for the intensity and the max KE of the ejected electrons. I'm sorry if my question didn't make sense. However, it would be nice to teach a "correct" false prediction made by the 19th century physicists :-). Perhaps this is a matter of historical physics.
>
> Regards,
>
> Antti Savinainen
> Finland