Bruggemann's formula \(n=\displaystyle\frac 12\sqrt{(3p-1)n_b^2+(2-3p)n_\nu^2+\sqrt{((3p-1)n_b^2+(2-3p)n_\nu^2)^2+8n_b^2n_\nu^2}}\), where \(n\) is the refractive index of the composite; \(p\) is porosity of the layer material; \(n_b\) and \(n_\nu\) are refractive indices of the bilk material and voids, respectively.
Average Weighted Value of Permitiviteis \(n^2=pn_b^2+(1-p) n_\nu^2\), where \(n\) is the refractive index of the composite; \(p\) is the volume fraction of voids; \(n_b\) and \(n_\nu\) are refractive indices of the bilk material and voids, respectively.
Average Weighted Value of Refractive indices \(n=pn_b+(1-p) n_\nu\), where \(n\) is the refractive index of the composite; \(p\) is the volume fraction of voids; \(n_b\) and \(n_\nu\) are refractive indices of the bilk material and voids, respectively.