A photon with wavelength 120 nm travels in vacuum toward a region containing free…
PHYSICS · Multi-part · A Level · Physics · Particles and radiation · Particles and radiation
Problem
A photon with wavelength 120 nm travels in vacuum toward a region containing free electrons that are initially at rest.
For calculations you may use h=6.63×10−34Js, c=3.00×108ms−1, and the electron mass me=9.11×10−31kg.
(a) Calculate the magnitude of the photon's linear momentum.
(b) An electron acquires the same amount of kinetic energy as the photon's energy. Determine the speed of that electron, assuming non-relativistic motion is an adequate approximation.
(c) Using your result from part (b), compute the magnitude of the electron's linear momentum.
(d) Compare the momenta from parts (a) and (c). Discuss which particle (photon or electron) carries more momentum for the same amount of energy and explain the physical significance of your result.