" The fact is, you can solve all the problems involving
photons using classical waves with quantized interaction.
This is done, for example, in the textbook
"Atoms and light" by John N. Dodd (Plenum Press, New York, 1991). "
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Интересная, может быть, книжка. Ну и что нам прописал доктор Джон Н. Додд? Если вкратце.
http://groups.google.com/group/sci.physics/msg/a3e6e5ea0b628492?hl=ru&=================================================
"Atoms and light" by John N. Dodd (Plenum Press, New York, 1991).
In Chapter 6, the Compton scattering is treated in an entirely classical
way, without using energy and momentum conservation, but just standard
classical em + relativistic *kinematics*, by the picture of a
circularly polarized em wave impinging upon a charged particle.
The calculation is based on deriving a steady-state solution for the
down-stream motion of the particle which is superimposed to the
constant rotation at the frequency of the passing wave.
I haven't read the analysis in detail, but my first impression is that
it is quite clever.
It is, especially in light of the comments at page 55, apparent that the
standard Compton effect, i.e. the one the Compton explained using the
notion of photon, does not actually *need* this notion.
So, according to the author, the standard (spin-free) Compton effect
cannot be invoked to argue the existence of photons.
I am sorry if some of you do not have access to this book, unfortunately
the author does not provide other references in which the calculation has
been presented.
That was very educational for me. I confess i did not know about this.
In Ch.12, p.144 the author also presents a critical treatment of the
photoelectric effect. Again, he does not only address the issue of
the "photonless" interpretation of the experiment, but also adds that
some subtle question which, at first sight, *could* lead to a photon
interpretation, actually does not.
I finally suggest the readig of Chapter 14, which contains quite of a
compelling criticism on the way this subject is _taught_.
Now i agree with Mati Meron on the fact that many other experiments that
support the photon picture and the QED exist, of course.
I never thought this was in question.
However, i must note that, at least from what i understood from this
thread, the main concern made by Martin Green was an "educational" one
and, from this point of view, i have frankly to agree with him.
Indeed, i can see in the process of *learning* about this subject, the
student risks to be exposed to some evident misconception.
Later on, she/he will (hopefully) learn more on the subject and gain a
deeper insight. But this does not justify the initial misconception.
The notion of photon is introduced quite early in the intro physics
courses. It may be true that some more accurate book does avoid to
invoke the mere, plain photoelectric effect as the evidence of the
photon's existence (although, honestly, i do know several intro-physics
books which carry this misconception).
However, at this point, i have no problem to recognize that this is the
first time i have read about a classical derivation of the Compton
effect. Honestly, i think that *really* this is not included in any
intro-level book, the ones student read while they are learning physics.
I think they all present, in a more or less open way, the standard Compton
effect as one compelling "demonstration" of the existence of photon and
not as an experiment that "supports" the photon's picture.
Please provide references, in the case my claim happens to be wrong.
Maybe the details of this argument may be of interest only to people who
study history of physics, considering that the photon picture has proven
to be successful in so many applications.
Needless to say, the very Compton effect has aspects that are not
correctly addressed by the semiclassical picture (e.g. effect of the
particle's spin) and lead, for example, to the QED Klein-Nishina
differential cross section as i said elsewhere (i hope at least this does
not have a classical derivation... :-) )
However, why should a student be told, even if it's just the beginning of
her/his studies in physics, that "the photon's existence has been
proved by the mere Compton effect" when it's not the case, in that the
Compton lends itself both to a classical derivation and "corpuscolar"
derivation ?
Is it true that the Compton effect is understood by so many students as a
"test" for the existence of photons ?
Thank you all for your contributions.
best regards
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