Physics Help Forum Question about a polarising filter.
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 Feb 14th 2010, 05:25 PM #1 Junior Member   Join Date: Feb 2010 Location: UK Posts: 17 Question about a polarising filter. DOUBLE POST, SORRY Explain how you could use a polarising filter to find out which surfaces polarise light when they reflect it. Brewster found that the surfaces that do this reflect completely polarised light when the tangent of the angle of incidence equals their refractive index. Calculate the angle of incidence needed to reflect completely polarised light for glass of refractive index 1.5. What is the angle of reflection for this light? The reflected light is only about 8%. The rest enters the glass. How might you boost this % using glass reflective surfaces only? Please explain how to do all parts of this question. All help very much appreciated! Don't even know where to start on this Thanks Last edited by George321; Feb 14th 2010 at 05:42 PM.
 Mar 1st 2010, 02:24 AM #2 Senior Member   Join Date: Dec 2008 Location: Udupi, Karnataka, India Posts: 292 Observe the reflected light form the surface through the polarizing filter. Now rotate the filter. If you see the variation in the intensity of the light, then the reflected light is polarized. At one instant, if you see zero intensity, the light is completely polarized. Use formula μ = tan(θp) You can increase the % by using stack multiple plates.

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