Another way in which the presence of dangling bonds affects the optical properties of a material is via polarization. For a material with dangling bonds, the absorption intensity depends on the polarization of the absorbed light. This is an effect of the symmetry in which the dangling bonds are distributed over the surface of the material. The dependence only occurs up to the energy at which an electron can be excited to the level of the gap but not to the valence band. This effect along with the polarization dependence disappearing after the dangling bonds have been annealed, shows that it is an effect of the dangling bonds and not just of the general symmetry of the material.