[en] Recently, there has been increased interest in near normal incidence optical systems for use in the soft x-ray domain (10A < λ < 100A). This region of the x-ray spectrum is important because many organic constituents have their Κ-absorption edges in this range. One important application of near normal incidence soft X-rays optical systems is lithography, for which 44.7A radiation is particularly well suited. Hence, the authors have concentrated their studies at this wavelength. Stacks of their alternating layers with low and high electron densities can be used to obtain mirrors with substantial reflection coefficients. The authors have developed a model to obtain the optical properties of such a stack in a fashion similar to that used for visible light. This model can be shown to be quite accurate for near normal incidence and for wavelengths long compared to the interatomic spacing. They have also shown from this model that a smooth, 200 layer, carbon-tungsten stack would provide a reflectivity of approximately 25% at 44.7A when used in normal incidence