The momentum of an electromagnetic wave inside a dielectric
  The problem of assigning a momentum to an electromagnetic wave packet propagating inside an insulator has become known under the name of the Abraham-Minkowski controversy. In the present paper we re-examine the question, first through a power expansion in the polarizability of the medium and assuming the simplest and most natural choice for the force exerted on a dielectric material by an electromagnetic field. It is shown that the Abraham expression is highly favoured. We then show the complete generality of these results. 
Massimo Testa
physics.class-ph hep-th physics.optics