Alternative method for wave propagation analysis within bounded linear   media: conceptual and practical implications
  This paper uses an alternative approach to study the monochromatic plane wave propagation within dielectric and conductor linear media of plane-parallel-faces. This approach introduces the time-averaged Poynting vector modulus as field variable. The conceptual implications of this formalism are that the nonequivalence between the time-averaged Poynting vector and the squared-field amplitude modulus is naturally manifested as a consequence of interface effects. Also, two practical implications are considered: first, the exact transmittance is compared with that given by the Beer's Law, employed commonly in experiments. The departure among them can be significative for certain material parameter values. Second, when the exact reflectance is studied for negative permittivity slabs, it is show that the high reflectance can be diminished if a small amount of absorption is present. 
Alberto Lencina, Beatriz Ruiz and Pablo Vaveliuk