Generalized Lorentz Law and the force of radiation on magnetic dielectrics

Research output: Chapter in Book/Report/Conference proceedingConference contribution

8 Scopus citations


The macroscopic equations of Maxwell combined with a generalized form of the Lorentz law are a complete and consistent set; not only are these five equations fully compatible with the special theory of relativity, they also conform with the conservation laws of energy, momentum, and angular momentum. The linear momentum density associated with the electromagnetic field is p EM(r,t)=E(r,t)×H(r,t)/c2, whether the field is in vacuum or in a ponderable medium. [Homogeneous, linear, isotropic media are typically specified by their electric and magnetic permeabilities εo ε(ω) and μoμ(ω).] The electromagnetic momentum residing in a ponderable medium is often referred to as Abraham momentum. When an electromagnetic wave enters a medium, say, from the free space, it brings in Abraham momentum at a rate determined by the density distribution pEM(r,t), which spreads within the medium with the light's group velocity. The balance of the incident, reflected, and transmitted (electromagnetic) momenta is subsequently transferred to the medium as mechanical force in accordance with Newton's second law. The mechanical force of the radiation field on the medium may also be calculated by a straightforward application of the generalized form of the Lorentz law. The fact that these two methods of force calculation yield identical results is the basis of our claim that the equations of electrodynamics (Maxwell + Lorentz) comply with the momentum conservation law. When applying the Lorentz law, one must take care to properly account for the effects of material dispersion and absorption, discontinuities at material boundaries, and finite beam dimensions. This paper demonstrates some of the issues involved in such calculations of the electromagnetic force in magnetic dielectric media.

Original languageEnglish (US)
Title of host publicationOptical Trapping and Optical Micromanipulation V
StatePublished - 2008
EventOptical Trapping and Optical Micromanipulation V - San Diego, CA, United States
Duration: Aug 10 2008Aug 13 2008

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherOptical Trapping and Optical Micromanipulation V
Country/TerritoryUnited States
CitySan Diego, CA


  • Electromagnetic theory
  • Momentum of light
  • Optical trapping
  • Radiation pressure

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


Dive into the research topics of 'Generalized Lorentz Law and the force of radiation on magnetic dielectrics'. Together they form a unique fingerprint.

Cite this