PLANE POLARIZED LIGHT BY REFLECTION

The simplest way to produce plane polarized light is by reflection. It was discovered by Malus in 1808 that partially polarized light is obtained when ordinary light is reflected from the surface of a transparent medium like glass or water and that the degree of polarization varies with the angle of incidence. At a certain angle of incidence, depending upon the nature of the reflecting surface, the reflecting light has the greatest percentage of the polarized light. This angle of incidence is called the angle of polarization for that medium and for ordinary glass its value is 57.5*. As the refractive index depends upon the wavelength, the angle of maximum polarization varies with the wavelength and hence the complete polarization is possible with monochromatic light and not with white light.