These relations link the macroscopic quantities such as the refractive index to the dipole polarization of the individual atoms or molecules. When the latter are kept apart the polarizing field is no longer the average electric field in the medium. Similarly for the pion, the lightest meson and the carrier of the long range part of the nuclear force, its typical non-relativistic scattering for individual nucleons has a dominant dipole structure with a known average dipole polarizability of strength ("the average scattering volume").