1 \begin{problem*}{28.16}
2 A $0.110\U{nm}$ photon collides with a stationary electron. After
3 the collision, the electron moves forward and the photon recoils
4 backward. Find the momentum and the kinetic energy of the electron.
5 \end{problem*} % problem 28.16
8 The photon scatters by $180\dg$, so from the Compton shift equation
10 \lambda' = \lambda_0 + \frac{h}{m_e c}(1-\cos 180\dg)
11 = \lambda_0 + \frac{2h}{m_e c}
12 = (110+4.85)\U{pm} = 115\U{pm} \;.
14 The kinetic energy of the electron is given by the change in photon
15 energy (just like problem 28.15).
17 K = E_0 - E' = \frac{hc}{\lambda_0} - \frac{hc}{\lambda'}
18 = 11.3\U{keV} - 10.8\U{keV}
21 We conserve momentum to find the electron's momentum, using
22 $p_\text{photon}=E/c$.
24 p_i &= \frac{E_0}{c} = p_f = p_e - \frac{E'}{c} \\
25 p_e &= \frac{E_0+E'}{c} = (11.3+10.8)\U{keV/$c$} = \ans{22.1\U{keV/$c$}}
26 = \ans{1.18\E{-23}\U{kg$\cdot$m/s}} \;.