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When we study the interaction of the electromagnetic radiation with free electrons we can find two different approaches in the literature: for low frequency (RF, light...) a classical view is used and it is said that the electrons oscillates due to the electric field of the wave, but for high frequency radiation (X-rays, gamma), the type of interaction seems totally different (Compton effect and the like) and radiation is usually modeled as "particles". For an radiation with "intermediate" frequency such as UV or very low energy X-rays, would interactions be "electric-like" or "compton-like"?. How is the transition between both regimens?

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You have to realize that the classical view emerges from underlying quantum mechanical view (particles). Nature is really in its foundations quantum mechanical but it is practical to use classical theories and models in the macro state , i.e. dimensionswhere hbar is effectively equal to zero as far as measurements go. –  anna v Jul 27 '13 at 19:02
    
I already assumed that, but how does exactly the classical oscillation emerge from particle-type (Compton) collisions? –  grux gru Jul 28 '13 at 11:23
    
i.e., what happens in the transition region (at an intermediate wavelength)? –  grux gru Jul 28 '13 at 11:30
    
Have a look at how classical fields emerge from quantum/particle ones: motls.blogspot.com/2011/11/… .you have to define intermediate region in debroglie wavelengths of the particle. Depending on the accuracy of measurement the particle/photon view will dominate of the classical em field/particle one. I think nano technology gives such orders of discrimination. watch the fuziness in these: youtube.com/watch?v=oSCX78-8-q0 . fuzziness is due to the qm uncertainties . –  anna v Jul 28 '13 at 12:08
    
good question ! –  guru Aug 11 '13 at 19:05
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1 Answer

Wave length.

When the wavelength is many times larger as the interacting particle, you use a field. When about the same size as the particle, field approach doesn't work that well, change to particles.

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Since the electron does not have a "size", the wavelength is always larger than the particle. Did you mean the wave associated to the particle?. Anyway, there should be a smooth transition between both kinds of behaviours or regimens. How is it possible taking in to account the differences between a classical oscillation an a compton collision? –  grux gru Jul 27 '13 at 17:48
    
there is the de Broglie wavelength for every particle: lamda=h/p , so there is always a wavelength to gauge whether it is practical to use classical or quantum em –  anna v Jul 27 '13 at 18:59
    
But how do you determine the 'size' of the interacting particle? Electron itself is defined by a wave packet and uncertainty in position depends on the specific type of measurements made. –  guru Aug 11 '13 at 19:08
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