Which statement best describes why two-dimensional momentum analysis is required when…
PHYSICS · Single correct · AP · Physics 2: Algebra-based · Modern Physics · Modern Physics
Problem
Which statement best describes why two-dimensional momentum analysis is required when an x-ray photon scatters from a free electron?
(a) Because the photon’s energy decreases after the collision, energy conservation can no longer be applied.
(b) Because the photon changes direction, its momentum components along two perpendicular axes must balance those of the recoiling electron.
(c) Because momentum is conserved only in the direction of the incident photon, transverse components need not be considered.
(d) Because a photon has zero rest mass, it cannot carry momentum perpendicular to its motion, so any sideways momentum must come solely from the electron.