Uses of Polaroids :
(1) Polaroids can be used to control the intensity, in sunglasses, windowpanes, etc.
(2) Polaroids are also used in photographic cameras and 3D movie cameras.
Thus a polaroid transmits only one component (parallel to a special axis). The resulting light is called linearly polarised or plane polarised. When this kind of light is viewed through a second polaroid whose axis turns through 2π, two maxima and minima of intensity are seen.