Incidence of an electromagnetic wave onto one or two interfaces under the conditions of transition from dielectric propagation to metallic propagation

Penetration of electromagnetic waves into a medium, as well as reflection, transmission, and absorption of waves by a plate with an arbitrary conductivity, is analyzed under the condition of transition from dielectric propagation to metallic propagation. Two types of transition criteria are proposed: a criterion based on the penetration depth and a criterion based on the behavior of the reflection coefficient as a function of the plate depth. It is found that the critical values of conductivity corresponding to different types of criteria differ by a factor of 2.7 +/- 0.3. High reflectivity of metal films with a thickness substantially less than the penetration depth is qualitatively explained. It is shown that the frequency of transition from the metallic type of wave propagation to the dielectric type increases as the prescribed value of the reflection coefficient decreases and the conductivity increases.