Answer
$\Delta K = 3.85\times 10^{-15}~J$
Work Step by Step
The change in kinetic energy of the electron is equal in magnitude to the change in energy of the photon. We can use conservation of energy to find the change in kinetic energy of the electron:
$\Delta K +E_f = E_0$
$\Delta K = E_0 - E_f$
$\Delta K = \frac{hc}{\lambda_0} - \frac{hc}{\lambda_f}$
$\Delta K = (hc)~(\frac{1}{\lambda_0} - \frac{1}{\lambda_f})$
$\Delta K = (6.626\times 10^{-34}~J~s)(3.0\times 10^8~m/s)~(\frac{1}{0.0100\times 10^{-9}~m} - \frac{1}{0.0124\times 10^{-9}~m})$
$\Delta K = 3.85\times 10^{-15}~J$
