Light absorption by a dipole

In semiclassical radiation theory, the electric dipole moment induced on an atom by a strong incident field, absorbs much more energy, per sec, than is flowing through its geometrical cross section. This means, the atom has the capability to “suck up” electromagnetic energy from a spatial region that is by far larger than its own volume. An intuitive understanding of this effect is provided by studying, in the framework of classical electrodynamics, the energy flow in the total field made up by superposition of the incident wave and the field that is generated by the dipole also in the absorptive case.