question_answer

What is a polaroid? How is plane polarised light obtained with its help? How will you use it to distinguish between unpolarised light and plane polarised light?           

Answer:

                A polaroid is a thin commercial sheet which makes use of the property of selective absorption to produce an intense beam of plane polarised light.  When unpolarised light falls on a polaroid, only the vibrations parallel to the transmission plane get trans-mitted and perpendicular vibrations are selectively absorbed. So the emergent light is plane polarised. When unpolarised light is seen through the polaroid the intensity of light is cut down to half due to polarisation of light. When the polaroid is rotated, the intensity of light does not change. When linearly polarised light is seen through a polaroid and the polaroid is rotated, the transmitted light shows rise and fall of intensity. The intensity becomes twice maximum and twice zero in each rotation.