# Compton scattering

1. Jan 26, 2009

### Charlie G

Is compton scattering the reason why different substance have different colors?

I was thinking along the lines of substanes with higher energy electrons around the atom wouldn't cause too much of a change in the photons wavelength and atoms with lower energy electrons will absorb more energy and would cause a more dramatic increase in wavelength.

I have thought of flaws in my thinking like why when shine a blue light on something the light doesn't comes back to my eyes green, which I have never known to happen. But I was really just wanting to know if Compton scattering contributes to color in any way? Most definitions only seem to talk of gamma quanta and x-rays, so maybe the effect only happens with such high energy photons so we could never see it with our own eyes, but I'm just curious.

2. Jan 26, 2009

Staff Emeritus
No. A quick proof: look at the Compton formula. Does the substance where you get the electron enter into it? If not, how can this determine the color?

3. Jan 29, 2009

### Charlie G

Yea good point, but could anyone tell me why one substance reflects blue light while the next one reflects green, whats the difference between two substances at the atomic level that causes them to be different colors?

4. Jan 29, 2009

### mathman

It is the transitions between energy levels within the atomic electron structure that determine the energy (frequency - color) of the emitted photons.

Compton scattering is scattering by "free" electrons.

5. Jan 29, 2009

### Charlie G

Oh I see, thx for the reply mathman.

6. Jan 29, 2009

### cesiumfrog

That's not a very good reason, since Compton scattering does depend on the effective mass of the electron.

Perhaps a better one is something like: red objects illuminated by blue light appear black (indicating the relevant process is absorption rather than colour shifting).

7. Feb 4, 2009

### lightarrow

Can you clarify this? What/how much is effective mass in this case?
Thanks.

8. Feb 4, 2009

### Naty1

Charlie...good question, not an obvious answer...some errors in posts above..
Suggest you read Compton scattering and Color via Wikipedia for an introduction....
color and selected types of Compton scattering do seem related.

Because there are different "Compton ccattering" mechanisms you probably want to specify what you mean...here is one qualification as an example:

and
http://en.wikipedia.org/wiki/Compton_scattering#Compton_scattering

9. Feb 4, 2009

### Charlie G

Thx for the reply Naty1. The pair production sounds really interesting, I think its really cool to find situations where energy becomes matter, rather than matter becoming energy. It really emphasizes energy-mass equivalence. Though its also kind of disturbing, ever since learning of energy-mass equivalence, my entire concept of mass is now blurred. But thats what makes physics so interesting:)

10. Feb 5, 2009

### malawi_glenn

Well, we had some major discussion last month regarding mass/energy. And also in this quite new thread: