As illustrated in Fig. , the relevant optical power balance equation is = + + + and ( --) corresponds to the extinction = + , which accounts for all the energy removed from a propagating beam in a far-field measurement. In this representation corresponds to the specular and to the diffuse reflectance respectively. Due to a zero transmittance = 0 of the MIM metasurface, both and manifest as a backward reflection of light. In the case of nanoparticles (nanodiscs in this work), their plasmonic resonance-related optical properties are derived from the Mie scattering by the structures. The the resonance bandwidth is defined by scattering rather than the inherently broadband absorption exhibited by electron plasmas in metals .