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## Main Question or Discussion Point

So when you calculate the scattered electron energy and the scattered photon energy (for 180 degree deflection) you get roughly the following (in keV).

Photon(in)__Photon(scattered)__Electron(recoil)

27.5_______24.8______________2.7

81_________62_______________19

140________91_______________49

364________150______________214

511________170______________341

1330_______214______________1116

infinity_____255.5_____________~infinity

So as the Photon(in) energy increases, the scattered photon energy approaches 255.5 keV (aka half of an electron's rest energy). And as the Photon(in) energy decreases, the scattered photon energy approaches the input energy. Why is this so?

For the high energy case, the best explanation I could come up with is that this is due to the conservation of the relativistic energy and/or the invariant mass of the system. In sort of the same way that two 255.5 keV traveling in opposite directions would be equal to an electron at rest. But this doesn't necessarily explain what is going on at the lower energies.

I've run through the equations too many times now and am still having a little trouble conceptualizing exactly what is going on in the low energy case. Any input would be appreciated.

Photon(in)__Photon(scattered)__Electron(recoil)

27.5_______24.8______________2.7

81_________62_______________19

140________91_______________49

364________150______________214

511________170______________341

1330_______214______________1116

infinity_____255.5_____________~infinity

So as the Photon(in) energy increases, the scattered photon energy approaches 255.5 keV (aka half of an electron's rest energy). And as the Photon(in) energy decreases, the scattered photon energy approaches the input energy. Why is this so?

For the high energy case, the best explanation I could come up with is that this is due to the conservation of the relativistic energy and/or the invariant mass of the system. In sort of the same way that two 255.5 keV traveling in opposite directions would be equal to an electron at rest. But this doesn't necessarily explain what is going on at the lower energies.

I've run through the equations too many times now and am still having a little trouble conceptualizing exactly what is going on in the low energy case. Any input would be appreciated.