If denotes an interface Fresnel reflection or transmission coefficient for - or -polarized light at an oblique angle of incidence , and z denotes the same coefficient at normal incidence, then it can be shown that w is an analytic function of , that depends parametrically on the angle of incidence . The inverse mapping between the complex and planes is illustrated here by one of the Fresnel coefficients (for s reflection) at one oblique angle of incidence (45°) and normal incidence. Here , where and are the oblique-incidence amplitude reflectance and phase shift.