Black Silicon, a surface modification of silicon, with needle like structures of about 10Ám, has low reflectance and correspondingly high absorptance in the visible and infrared range of wavelengths making it more viable than crystalline silicon for applications in silicon optoelectronics. Like crystalline Si, black silicon has potential applications in solar cells, sensors, antibacterial surfaces and offers new opportunities. In this study, the optical properties of black silicon, in the visible, near and short wavelength infrared region, are simulated based on the effective medium approximation. The application of Helmholtz’s law of optical reciprocity to the two layer medium of black silicon on crystalline silicon is examined. The change in optical properties for Black Silicon with a layer of native oxide is studied.