# Does the photon emitted by an electron falling to a lower energy level have a direction?

When an electron falls from an energy state to a lower one, electromagnetic radiation is emitted. Is this equally emitted in all directions (as a spherical wave) and can we only give it a direction after it is detected at some location in the form of a photon, or is it/can it be emitted in a more definite direction?

If the first case is correct, is it true that after emitting the photon the change in momentum of the electron (or the system to which it belongs) is a spherically symmetric superposition which collapses into a definite direction when the photon is received somewhere?

Depends on a theory. In semi-classical radiation theory, neo-classical theory or in stochastic electrodynamics, radiation is described by continuous EM field. The radiation from one transition should be approximately that of a dipole - it has polarization and angular characteristics of a dipole radiation. The phase of the radiation moves out as spherical wave, but the intensity is strongest in the plane perpendicular to the transition dipole matrix element $\boldsymbol{\mu}_{12}$.