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An easy method to determine the plane of polarization of a light beam

Many a time, we need to determine the plane of polarization of linearly polarized light. This could simply be the light issued from a laser or emerging from a polarizer. We utilize a simple method which we describe below and demonstrate in the accompanying video.

We prepare a solution of 4.5 micron polystyrene microspheres. We have about 100 million spheres in one mL. We take about 5 mL of this solution inside a cuvette or glass vial. Laser light traverses this solution and we view the glow emerging from the vial at right angles to the propagation direction. P polarized (or horizontally polarized) light will be absent from the scattered ray at this viewing angle. This results in diminished glow.

If the input beam is S or vertically polarized, the scattered ray at 90 degrees will be of maximal intensity. Intermediate glows can be seen for mixtures of horizontal and vertical. This separation of polarizations in scattered and transmitted light is in fact important in imparting colors to the atmosphere.

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Muhammad Sabieh Anwar (Personal)

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Dr Muhammad Sabieh Anwar is an Associate Professor of physics at the LUMS Syed Babar Ali School of Science and Engineering. He helped establish the physics department and was among the principal founders of the School’s experimental facilities and curriculum. He remained Chair of the Physics Department for a period of five years. Ideas from his physics instructional laboratories have been replicated in five Pakistani universities.

His research interests encompass spintronics, magnetism and optics. Sabieh has published around eighty research articles in international journals including Science and Physical Review Letters. He is the General Secretary of the Khwarizmi Science Society which is aimed at popularization of science at the grassroots levels. Prior to joining LUMS SSE in 2007, Sabieh was a post-doc in chemistry and materials science at University of California, Berkeley and a PhD student, as Rhodes Scholar, at the Oxford University. He is the recipient of the TWAS medal in physics in 2008 and the National Innovation Prize in 2015.

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