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Polarization. PHYSICS 1. Natural Radiation. Somnath Bharadwaj and Pratik Khastgir, Department of Physics and Meteorology, IIT Kharagpur, 721 302 India http://www.cts.iitkgp.ernet.in/~phy1/. Linear Polarizer. Mallus;s Law. Producing Linear Polarization. Dichroism or selective absorption
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Polarization PHYSICS 1 Natural Radiation • Somnath Bharadwaj and Pratik Khastgir, Department of Physics and Meteorology, IIT Kharagpur, 721 302 India http://www.cts.iitkgp.ernet.in/~phy1/
Producing Linear Polarization • Dichroism or selective absorption • Scattering • Reflection • Birefringence or double vision
Dichroism Wire-mesh polarizer
Dichroic Crystals Tourmaline – coloured crystal
Polaroid H sheet • Possibly most commonly used polarizer • Inventor E H Land in 1938 • Polyvinyl alcohol sheet heated and stretched • Dipped in iodine rich ink • Iodine chains along direction of stretching • Acts like a wire mesh
Brewster’s Law Brewster’s angle
Birefringence • Occurs in anisotropic crystals • Refractive Index ne when E along x axis • Refractive Index no when E perp. to x axis • Optic axis along x • Uniaxial Crystal
Birefringence positive