Energy-Momentum Tensor and Related Experimental Analysis of Electromagnetic Waves in Media

TL;DR

This paper develops a unified energy-momentum tensor for electromagnetic waves in media, explaining experimental results and clarifying the roles of Minkowski and Abraham momenta, with implications for light applications.

Contribution

It introduces a new energy-momentum tensor that unifies Minkowski and Abraham momenta, providing a comprehensive theoretical framework for electromagnetic waves in media.

Findings

Unified energy-momentum tensor derived for electromagnetic waves in media

The tensor explains experimental results like light pressure and fiber deformation

Minkowski momentum is a canonical momentum; Abraham is a mechanical momentum

Abstract

We find that the energy-momentum tensor of electromagnetic waves in media is very similar to that of ordinary fluids, and concepts such as density, pressure, and energy transfer rate can be similarly defined. On this basis, we conducted a detailed theoretical analysis on the mean momentum and equivalent mass of photons in the medium, the relationship between pressure and polarization of beams, the influence of polarization energy and magnetization energy of the medium, the Bernoulli effect of beams and the energy-momentum tensor of beams in moving media. We also obtain a conservation new energy-momentum tensor based on the interaction term between the electromagnetic field and the medium. From this energy-momentum tensor, we can derive both the Minkowski momentum and the Abraham momentum simultaneously. We find that Minkowski momentum is actually a canonical momentum that considers the influence of the interaction between electromagnetic waves and media, while Abraham momentum is actually a mechanical momentum that does not consider the influence of the interaction between electromagnetic waves and media. Based on the theory obtained in this paper, we have provided theoretical explanations for Jones'experiment of light pressure in a medium, Ashkin's free liquid surface deformation experiment, Weilong's optical fiber deformation experiment, and frequency shift measurement experiment. The theory obtained in this paper can self-consistently explain the above experiments simultaneously. Unlike the Minkowski and Abraham tensors, according to the energy-momentum tensor proposed in this paper, a beam in a medium also generates a pressure on its side, and the direction of this pressure is related to the polarization of the beam. The findings of this paper may shed new light on the application of light.