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Radiation pressure and the distribution of electromagnetic force in dielectric media

A detailed distribution of the force of electromagnetic radiation in and around dielectric media can be obtained by a direct application of the Lorentz law of force in conjunction with Maxwell's equations. We develop a theory of the force exerted by a focused light beam on the free surface as well as within the volume of a transparent dielectric medium. Although the medium can be either solid or liquid, here we emphasize the application of the formulas to liquids since, in principle at least, surface deformations and liquid motions are measurable. Our theory predicts that, upon entering the liquid from the free space, the beam of light exerts an outward vertical force on the entrance surface that tends to produce a localized bulge. This surface force, however, is much weaker than that predicted by prevailing theories and, in contrast to current beliefs, is found to depend on the polarization state of the incident beam. Within the volume of the liquid we predict that the forces of radiation tend to create four counter-rotating vortices at the four corners of the focused spot; the sense of rotation within these vortices depends on the direction of the incident polarization. These striking departures from conventional wisdom with regard to the force of radiation arise from a revision in the form of the Lorentz law as applied to the bound charges/currents within a dielectric medium.