Demonstrating a Quantum Phenomenon with Polaroid Sunglasses The insertion of Polaroid sunglasses at an oblique angle between two crossed Polaroid sheets permits light to come through. The shape of the sunglasses is bright hut surrounded by darkness. The effect is the more striking because one is accustomed to thinking of Polaroid sunglasses as absorbing light, yet this absorbing material causes more light to be transmitted under these circumstances. This demonstration can be used to show that measuring'devices for quantum mechanical properties sometimes change.the state of systems on which they operate. In this instance the inserted Polaroid changes the direction of polarization of the photons that it transmits. I t leaves them in the eigenstate associated with the Polaroid. The usual vector explanation of the demonstration, though useful for a quantitative treatment, distracts from this creation of a new state by emphasizing the ahsorption of one of the components of the original polarization vector. This demonstration can serve as a striking introduction to other demonstrations that use polarized light to illustrate quantum mechanical concepts.l 'Cadton, T. S.,Arner. J Phys., 42,408 (1974) Oberlin College Oberlin. Ohio 44074
322 / Journal of Chemical Educatbn
Terry S. Carlton
