Answer
$\Delta \lambda = 2.43\times 10^{-12}~m$
Work Step by Step
We can find the Compton shift $\Delta \lambda$:
$\Delta \lambda = \frac{h}{mc}(1-cos~\phi)$
$\Delta \lambda = \frac{h}{mc}(1-cos~90^{\circ})$
$\Delta \lambda = \frac{h}{mc}$
$\Delta \lambda = \frac{6.63\times 10^{-34}~J~s}{(9.109\times 10^{-31}~kg)(3.0\times 10^8~m/s)}$
$\Delta \lambda = 2.43\times 10^{-12}~m$
