To understand how polarizers work, we must first understand what light polarization is. When a light beam moves through space, it is made up of electric and magnetic fields that point in a plane perpendicular to the direction the light is traveling, and that oscillate in their magnitude and direction. The exact axis of the electric field within the plane perpendicular to motion is in general random. And in the case of lots of randomly generated light going in the same direction, the axis of the electric field will almost certainly not be consistent. This is called unpolarized light. Sometimes, however, the electric field axis is consistent. When this happens, the light is said to be polarized along a certain direction—namely, the direction of the oscillating electric field. One can control the polarization of light by using a polarizer. There are a variety of polarizers, and just as many ways that they work. The simplest type is an absorptive polarizer, which does exactly what you’d expect it to: these polarizers transmit light polarized along one axis, and absorb light polarized perpendicular to that axis. The net effect is to remove (absorb) between some and all the light incident on this object that is polarized in any direction other than the polarization axis– the amount that is absorbed is a function of the angle between the light polarization and the polarization axis of the polarizer. This means that only the light polarized along the polarizer’s axis will pass through, and the light that passes through is now polarized even if the initial beam was not.