Brewster, Sir David (1781-1868), a Scottish scientist, is best known for the law named in his honor, Brewster's law. This law relates the amount that light is polarized to the refractive index of the medium the light is passing through. Polarized light consists of light waves that have a simple, orderly arrangement. The refractive index of a medium equals the velocity (speed in a particular direction) of light in a vacuum divided by the velocity of light in the medium. The indexes of most kinds of glass are around 1.5 to 1.6. See Polarized light.