Quantitative investigation of the validity conditions for the Beckmann–Kirchhoff scattering model

Approximate and rigorous methods are widely used to model light scattering from a surface. The boundary element method (BEM) is that accounts for polarization multiple effects. BEM suitable the scattered surfaces with complex geometries containing overhangs re-entrant features. Beckmann–Kirchhoff (BK) model, which an approximate can be predict behavior of slowly varying surfaces. Although BK cannot applied surface give rise effects, it has been field due its fast simple implementation. While many models restricted features relatively small height variations (typically less than half wavelength incident light), large variations, as long locally flat curvatures. Thus far, attempts have made determine validity conditions model. primary condition radius curvature any irregularity should significantly greater light. However, most accurate results quantifying critical. This work aims quantify according different specifications, e.g., slope angles (SA) For this purpose, fields various sinusoidal combinations profiles simulated using their differences compared. result shows fails when there high SA ( ⪆ 38 deg) radii ⪅ 10 λ) within profile. Moreover, shown combination valid maximum angle value if average positive low 5 deg).