Past exam of the particle and nuclear physics course of the University of Cambridge / 2014 / Paper 1 / 4 / b / Solution

The symbols $EL$ and $ML$ mean electric and magnetic radiation multipoles of order $L$. The orders $L=1,2,3$ are called dipole, quadrupole and octupole. They describe the angular structure of charge/current radiation and the total angular momentum carried by the radiation; they do not change the photon's intrinsic spin from one. A real single photon has no monopole radiation mode.