A beam of X–ray photons with wavelength is incident on a target containing free
PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Modern Physics · Modern Physics
Problem
A beam of X–ray photons with wavelength 0.080nm is incident on a target containing free, stationary electrons. Some of the photons are observed to scatter through an angle of 60∘ relative to the incident direction.
Throughout this problem you may assume that the electrons are initially at rest and that any binding energies are negligible compared with the photon energies involved.
Use the information above to answer the following questions.
(a) Describe, in words, how conservation of energy applies to a collision between a single incident photon and a free electron. Identify the forms of energy that must be accounted for both before and after the collision.
(b) Without performing detailed numerical calculations, explain qualitatively how the kinetic energy of the recoil electron would change if the scattering angle of the photon were increased from 60∘ to 120∘. Justify your answer in terms of changes in photon wavelength and energy.
(c) Three individual scattered photons from the same X–ray beam are detected with wavelengths 0.082nm, 0.084nm, and 0.081nm. Rank the corresponding kinetic energies of the three recoil electrons from largest to smallest and provide a brief justification for your ranking.