A Certain Photon After Being Scattered from a Free Electron

Multiple Choice

A certain photon after being scattered from a free electron at rest moves at an angle of 120° with respect to the incident direction. If the wavelength of the incident photon is 0.611 nm, what is the kinetic energy of the recoiling electron?

A) 1.5 × 10^-18 J
B) 2.1 × 10^-18 J
C) 3.1 × 10^-18 J
D) 4.3 × 10^-18 J
E) 5.2 × 10^-18 J