Polarization of Light

The effect of crossed and uncrossed polarizers on a light beam is demonstrated.

Discussion

As we have demonstrated with a Slinky™, transverse waves are polarized. A polarizing sheet, such as Polaroid®, selectively transmits those components of light waves that are polarized parallel to the direction of one axis of the sheet and absorbs those polarized perpendicular to this axis. When unpolarized light of intensity I₀ passes through a polarizing sheet, the light transmitted has a plane of polarization parallel to the axis of the sheet and its intensity is 1/2 I₀.

A second polarizing sheet will pass essentially all the plane polarized light from the first if its axis is parallel to that of the first filter, but if its axis is at right angles to that of the first, the second sheet will absorb all of the light.

These results are consistent with modeling a beam of light as a collection of countless transverse waves with randomly oriented planes of polarization. Such light is said to be unpolarized; there is no single plane of polarization.