A physics research team investigates photon scattering from free electrons
PHYSICS · Multi-part · A Level · Physics · Particles and radiation · Particles and radiation
Problem
A physics research team investigates photon scattering from free electrons. In their lab notebook they write,
“Plotting the wavelength shift of the photon, Δλ=λs−λ0, against the quantity (1−cosθ) produced an almost perfectly straight line that passed near the origin.”
Answer the following questions about this observation.
(a) Explain, without performing detailed algebra, why a straight-line relationship between Δλ and (1−cosθ) is theoretically expected for photons scattered by free electrons at rest.
(b) Identify the physical constant that is revealed by the slope of the straight line. Describe the procedure an experimenter would follow to extract a numerical value for that constant from the graph.
(c) Give two distinct experimental or theoretical causes that could make individual data points deviate systematically from the straight line. For each cause, state whether it would tend to make the measured slope larger or smaller than the ideal value and justify your reasoning.