# The range of Klein-Nishina formula

1. Dec 1, 2013

### bobie

I found a nice applet: http://www.kcvs.ca/site/projects/physics.html
to study that formula, but it has a limited range.
Do you know of a better app or of a site where I can get results of real experiments?,
can someone tell me:

- does it work at all frequencies, or does it break down somewhere?
- is there a threshold over which the photon cannot be scattered at 180Â°?
- as the electron is inside a metal, can its recoil angle and speed really be observed and measured, or is it derived from the formula?
- if the energy is low , around 5.11 eV (1.2*1015 hv) what is roughly the speed of the electron ? I mean: does it get energy only from the photon (in the range of 0.0001 eV)?

Last edited: Dec 1, 2013
2. Dec 1, 2013

### mathman

Klein-Nishina is the formula for interaction between photons and free electrons. Its application is mainly for gamma rays where the electron binding energy can be ignored. At lower energies (X-rays etc.) other effects predominate.

3. Dec 2, 2013

### bobie

Thanks, mathman,
so it has a limited range of validity. Has the angle of recoil and speed of the free electron ever been verified?, what is the accuracy of the theoretical formula?
What happens if the energy of the gamma ray is thousand times the rest mass: the photon should
continue in its direction pushing the electron like a cannonball a pingpong ball, but the photon is always faster, then should be reflected. Can an electron act like a wall to a photon , say, 10^30 hv?

4. Dec 2, 2013

5. Dec 3, 2013

### bobie

thanks, mathman, your link is very useful, though somewhat difficult for me:I'll try to digest it, but at a first examination it seems that there is nochance of measuring the recoil angle and the momentum/energy of the electron. Is that correct?

6. Dec 3, 2013

### mathman

The Klein-Nishina formula gives the probability distribution of the outgoing photon angle with respect to the incoming direction.