A detailed study of the optical properties of amorphous silicon prepared by various methods is presented here. Comparisons of the various major optical parameters like the refractive index and the optical gap and related properties are then made for amorphous silicon films prepared by glow‐discharge, chemical vapor deposition, and sputtered films. Experimental observations of a linear variation of the static refractive index with the Urbach tail parameter for boron‐doped chemically vapor deposited films have been analyzed. Wherever relevant, spectroscopic and band‐structural models like those of Penn and Wemple and DiDomenico are employed to evaluate the optical parameters of the materials. We also examine briefly the optical properties of amorphous silicon dioxide. Extrapolation of conventional models are then made to derive the relevant optical parameters of SiO2.