Analytic Comparison of Reflection-based and Transmission-based Absorptances for Planar Materials

In this study, reflection-based and transmission-based absorptances of normally incident electromagnetic waves for planar materials were theoretically derived. The reflectance, transmittance, and absorptance of dielectric and magnetic absorbing materials were then compared using analytical equations. In the case of dielectric absorbers, the difference between the reflection-based and transmission-based absorptances is more pronounced at lower frequencies; this persists across several gigahertz. However, as regards magnetic absorbers, the differences were insignificant. Furthermore, a three-dimensional numerical simulation was performed to verify the accuracy of the analytical results.