Geometric visualization of the Brewster angle from dielectric--magnetic   interface
  A geometric visualization is presented for the Brewster angle for a plane wave reflecting from an interface. The surface is assumed isotropic but it is allowed to display both dielectric and magnetic susceptibility, and hence the Brewster (polarizing) angle can attain any value between 0 and 90 degrees, and can exist for both parallel and perpendicular polarizations. The geometric construction (a tetrahedron) is spanned by the basic material parameters of the surface. The Brewster angle appears in one of the faces of the tetrahedron. 
Ari Sihvola