This question on light waves was popular among the candidates and was well attempted
  The expected answers are:
    (a)  Waves other than light that can be plane polarized
            Radio waves
            X  - rays
            § – rays
             Ultraviolet rays
              Infrared rays.
   (b)    Methods of polarizing an unpolarized light
             -   Reflection(from smooth surface)
              -  Double refraction(through crystals)
              -   Selective absorption(in certain crystals)
               -   Scattering (by small particles)
               -    Polaroid.