Electric Charges Scatter Light

  • Thread starter zoobyshoe
  • Start date
  • #1
zoobyshoe
6,551
1,287
Reading about the double slit experiment in Six Easy Pieces I came across something I had questions about, which is how they detect whether an electron has gone through one slit or the other:

"To our electron apparatus we add a very strong light source, placed behind the wall and between the two holes, as shown in Fig. 6-4. We know that electric charges scatter light. So when an electron passes, however it does pass, on its way to the detector, it will scatter some light to our eye, and we can see where the electron goes."

p.127

I am wondering what the explanation is for this effect (the effect being: electric charges scatter light), if it has a name, and if it means that photons have a charge or if the electron is interacting with it electromagnetically, or if something else is going on. Is this actually visible with the naked eye? If so, what does it look like? History? Anyone know who discovered this? Somehow, I've never run across mention of this effect before.

(I'm asking this effect in and of itself, not in its implications to the double slit, which Feynman covers to my satisfaction.)
 

Answers and Replies

  • #2
ZapperZ
Staff Emeritus
Science Advisor
Education Advisor
Insights Author
35,995
4,714
zoobyshoe said:
Reading about the double slit experiment in Six Easy Pieces I came across something I had questions about, which is how they detect whether an electron has gone through one slit or the other:

"To our electron apparatus we add a very strong light source, placed behind the wall and between the two holes, as shown in Fig. 6-4. We know that electric charges scatter light. So when an electron passes, however it does pass, on its way to the detector, it will scatter some light to our eye, and we can see where the electron goes."

p.127

I am wondering what the explanation is for this effect (the effect being: electric charges scatter light), if it has a name, and if it means that photons have a charge or if the electron is interacting with it electromagnetically, or if something else is going on. Is this actually visible with the naked eye? If so, what does it look like? History? Anyone know who discovered this? Somehow, I've never run across mention of this effect before.

(I'm asking this effect in and of itself, not in its implications to the double slit, which Feynman covers to my satisfaction.)

Example: Compton scattering.

Zz.
 
  • #3
zoobyshoe
6,551
1,287
ZapperZ said:
Example: Compton scattering.

Zz.
Thanks, Zz. Google has a wealth of information now that I know the name of it.
 
  • #4
Meir Achuz
Science Advisor
Homework Helper
Gold Member
3,605
167
The low energy, long wavelength, scattering of a photon by an electron can be treated classically. It is called "Thomson scattering", and is given in most interemediate UG or grad EM txts.
 
  • #5
Gokul43201
Staff Emeritus
Science Advisor
Gold Member
7,176
21
Yes, I was going to say (to Zoob) that it's a useful thing to have the classical picture in your head. Watch me wave my hands :

EM wave incident upon charged particle ---> charged particle accelerated by (sinusoidal) Lorentz force ---> oscillating charge radiates in all directions and decays to ground state ---> radiated energy ~ absorbed energy ---> scattering = light absorbed and re-radiated at (nearly) same frequency but different directions
 
  • #6
zoobyshoe
6,551
1,287
Meir Achuz said:
The low energy, long wavelength, scattering of a photon by an electron can be treated classically. It is called "Thomson scattering", and is given in most interemediate UG or grad EM txts.
Indeed, Meir Achuz, googling "compton scattering" lead me to "Thompson Scattering" and "Rayleigh Scattering". The Thompson scattering seemed most to be describing the scattering mentioned by Feynman, and I was struck by how "classical" all of them were.
 
  • #7
zoobyshoe
6,551
1,287
Gokul43201 said:
EM wave incident upon charged particle ---> charged particle accelerated by (sinusoidal) Lorentz force ---> oscillating charge radiates in all directions and decays to ground state ---> radiated energy ~ absorbed energy ---> scattering = light absorbed and re-radiated at (nearly) same frequency but different directions
A nice nutshell version, Gokul.
 
  • #8
DaTario
928
30
Gokul43201 said:
Yes, I was going to say (to Zoob) that it's a useful thing to have the classical picture in your head. Watch me wave my hands :

EM wave incident upon charged particle ---> charged particle accelerated by (sinusoidal) Lorentz force ---> oscillating charge radiates in all directions and decays to ground state ---> radiated energy ~ absorbed energy ---> scattering = light absorbed and re-radiated at (nearly) same frequency but different directions

I would add to the above scheme, in the last step, that the scattered wave is born from the interference between the first incoming EM wave (the no absorbed part of it) and the re-radiated wave.

Best Regards

DaTario
 
  • #9
mmwave
211
2
By the way, it's the scattering of light that makes the sky blue and sunsets red, so you can see it. In that case though it is nitrogen and oxygen molecules doing the scattering.

mmwave.
 

Suggested for: Electric Charges Scatter Light

Replies
11
Views
321
  • Last Post
Replies
8
Views
327
  • Last Post
Replies
1
Views
543
  • Last Post
Replies
3
Views
380
  • Last Post
Replies
3
Views
357
  • Last Post
Replies
4
Views
352
  • Last Post
Replies
2
Views
368
Replies
1
Views
343
Replies
4
Views
447
  • Last Post
Replies
15
Views
443
Top