1. The problem statement, all variables and given/known data An X-ray photon is scattered at an angle of θ = 180.0° from an electron that is initially at rest. After scattering, the electron has a speed of 4.67 x 106m/s. Find the wavelength of the incident X-ray photon. 2. Relevant equations hc/λ = hc/λ′ + KE λ′ = λ + h/mc (1-cosθ) 3. The attempt at a solution Ok, I solved the first equation for λ′and set both equal to each other: hc/λ = hc/λ′ + KE λ′= λ + (λ/hc)KE (hopefully my algebra isn't off...could somebody check?) λ + (λ/hc)KE = λ + h/mc (1-cosθ) (subtract λ from both sides) (λ/hc)KE = h/mc (1-cosθ) (multiply both sides 1/KE) λ/hc = [h/mc (1-cosθ)]/KE (multiply both sides by hc/1) λ = [h∧2/m(1-cosθ)]/KE then plug in numbers.... But, do I have it right so far?