Thomson Scattering -- elastic collisions conundrum

In summary, the Thomson scattering effect is described as the changing electric field of an accelerating electron which carries energy that radiates out in all directions. However, it is observed that the energy of detected photons is not lower in wavelength as expected, indicating that the energy is not evenly spread out in all directions. Further investigation is suggested, using the classical approach and Maxwell's equations to understand electromagnetic radiation.
  • #1
C-Science
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Teacher described the Thomson scattering effect through the lens of the electric field changing as a moving particle is accelerated. The changing electric field of the electron accelerating carries with it an amount of energy, and this energy radiates out from the acceleration event. (there were more details but thats the gist I got)

I'm ok with this.

but since the electric field radiates out in all directions, the energy of the Efield shift should be spread out in all directions (this is where I think my thought process might be wrong, but I dont understand why) And if the energy is spread out, the energy of detected photons released along the wave front should be lowered by a factor of the angle of the detector - this would yield an elastic collision, but detected photons would be lower in wavelength. BUT detected photons are the same wavelength for Thomson scattering.. so it seems as all the energy of the collision is not released over a spherical surface, but in a specific direction, which denies the energy spreading out from the acceleration event in all directions of the E field. help?
 
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I would say that a) there are no photons in classical EM (photons are part of the QM theory of light); and, b) generally you need to look at Maxwell's equations to understand EM radiation.
 
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  • #3
C-Science said:
but since the electric field radiates out in all directions, the energy of the Efield shift should be spread out in all directions
This doesn't necessarily have to follow. Best to do what @PeroK suggests and use the classical approach (there's nothing naughty about that!)
 
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FAQ: Thomson Scattering -- elastic collisions conundrum

What is Thomson Scattering?

Thomson Scattering is the elastic scattering of electromagnetic radiation by a free charged particle, typically an electron. It is named after J.J. Thomson, who first described the phenomenon. This scattering process is a key mechanism in various fields such as plasma physics and astrophysics.

Why is Thomson Scattering considered elastic?

Thomson Scattering is considered elastic because the energy of the incident photon is conserved in the scattering process. The photon changes direction but retains its energy, meaning there is no energy transfer between the photon and the electron.

How does Thomson Scattering differ from Compton Scattering?

Thomson Scattering differs from Compton Scattering primarily in the energy regime of the incident photons. Thomson Scattering occurs when the photon energy is much less than the rest mass energy of the electron, resulting in no change in photon energy. In contrast, Compton Scattering involves higher energy photons, leading to a transfer of energy between the photon and the electron, and a corresponding shift in the photon's wavelength.

What are the applications of Thomson Scattering?

Thomson Scattering is widely used in plasma diagnostics to measure electron densities and temperatures. It is also used in astrophysics to study the properties of cosmic microwave background radiation and the interstellar medium. Additionally, it plays a role in laboratory experiments involving high-energy lasers and particle accelerators.

What are the limitations of Thomson Scattering?

The primary limitation of Thomson Scattering is that it is only applicable to low-energy photons. For high-energy photons, Compton Scattering becomes significant, complicating the analysis. Additionally, Thomson Scattering requires a relatively low density of electrons to avoid multiple scattering events, which can obscure the results.

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