# Compton Effect

1. Dec 6, 2006

### lightarrow

I know this topic has already been covered many times, but, is it possible to explain classically or semiclassicaly the standard Compton effect?

2. Dec 7, 2006

### octol

I remember reading once in some Quantum optics text that the standard Compton effect (together with the simplest form of the photoelectric effect) can indeed be explained semiclassically, i.e using quantum theory for matter and classical fields for EM. This was of course not recognised at the time though.

Don't remember the details or where I read it unfortunately :(

3. Dec 7, 2006

### dextercioby

What is the standard definition of the "standard Compton effect" ? I mean, what is the "effect" in the "Compton effect" ?

Daniel.

4. Dec 7, 2006

### lightarrow

$$\lambda\prime-\lambda=\frac{h}{m_ec}(1-cos\theta)$$

With "standard" I mean without considering the electron's spin.

Last edited: Dec 7, 2006
5. Dec 7, 2006

### dextercioby

Okay, then, so it's the shift in wavelength. IIRC, in high-school physics the treatment is semiclassical, or almost classical: the electron & the photon are assumed classical relativistic particles (i.e. always on their mass-sheet) and then E=h\nu for the photon is used and the shift is calculated imposing conservation of energy and momentum.

But to get back on topic, explaining the effect would require explaining what a photon is: and that can't be done without doing/knowing the quantization procedure for the em field. As for the quantized electron field, it's useless to think of the classical electron interacting with the quantized em field, so

Daniel.

6. Dec 7, 2006

### lightarrow

Sorry, I didn't explain well. I intended with light treated as a classical EM field.

7. Dec 8, 2006

### dextercioby

It can't be done.

Daniel.

8. Dec 8, 2006

### dupont

I have been thinking about this lately in the context of momentum loss of radiation upon passage through a diluted plasma. Momentum loss from stationary plasma should red-shift radiation. I found that there is no momentum transmitted from radiation field to electron if the em field is linearly polarised.

[OOOPS! I apologize. In replying to your post, I accidentally hit "edit" instead of "quote" and permanently edited your post. I can't seem to get the buffer to repost your entire original message. Oy! - Zz]

Last edited by a moderator: Dec 8, 2006
9. Dec 8, 2006

### lightarrow

So, what did they talk about?:

http://www.usenet.com/newsgroups/sci.astro/msg02581.html:
(Edit: this url doesn't work anylonger, at least from my server.)
Quote:
<<You should take a look at
"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. >>

Unfortunately I don't have that book, so I can't make any comment.