Page 3: Research news on electromagnetic reflectance and emissivity

Electromagnetic reflectance and emissivity are complementary radiative properties describing how materials interact with incident and thermally emitted electromagnetic radiation as a function of wavelength, polarization, and angle. Reflectance quantifies the fraction of incident radiant flux reflected by a surface, decomposable into specular and diffuse components and governed by Fresnel relations and surface roughness. Emissivity is the ratio of a surface’s spectral radiance to that of an ideal blackbody at the same temperature, constrained by Kirchhoff’s law such that, under thermal equilibrium, spectral emissivity equals spectral absorptance. Together, these properties are fundamental for radiative transfer modeling, remote sensing retrievals, thermal infrared imaging, and energy balance analysis.