2. Polarized light

Light is said to be "plane polarized" (figure 3 ) when the electric field associated with it travels in the same plane. Of course, the magnetic field remains in a plane perpendicular to the previous one. The term "rectilinear polarization" is sometimes used.

Unpolarized light, such as so-called "natural" light, is made up of lights randomly polarized in all directions (figure 4 ); each successive wave moves in a different plane.