Griffiths Introduction to Elementary Particles · Problem 10.9
Weak Interactions — David J. Griffiths
Physics — QFT · wavelength-probe-target
Problem
Show that in both the electromagnetic (electron-proton scattering) and weak (neutron beta decay) cases, the wavelength of the ``probe'' (γ or W, as the case may be) is much larger than the diameter of the ``target'' (p or n).