Question SPM.1A.HL.TZ0.35

A photon of wavelength $\lambda$ scatters off an electron at rest. The scattered photon has wavelength $\lambda \text{'}$.

What is the fraction of the incident photon energy that gets transferred to the electron?

A.  $\frac{\lambda }{\lambda \text{'}}$

B.  $\frac{\lambda \text{'}}{\lambda }$

C.  $\frac{\lambda \text{'}-\lambda }{\lambda }$

D.  $\frac{\lambda \text{'}-\lambda }{\lambda \text{'}}$