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.