Inhomogeneity thumb|alt=Illustration with gradually bending rays of light in a thick slab of glass|A gradient-index lens with a parabolic variation of refractive index () with radial distance (). The lens focuses light in the same way as a conventional lens.
inhomogeneity thumb|alt=illustration with gradually bending rays of light in a thick slab of glass|a gradient-index lens with a parabolic variation of refractive index () with radial distance () the lens focuses light in the same way as a conventional lens