Hallo
I don't understand why I can't use
Δλ = λ'- λ = h/(m·c) · ( 1 - cos φ )
and ΔE = h · c / Δλ
for getting the energy ΔE which is transferred to the electron
In school we did it like this: 1/f'- 1/f = h/(m·c) · ( 1 - cos φ )
<-> E' = hf' = hf/(1 + hf(1 - cos φ )/(mc^2))...