Fig. (2).

Simplified sketch of one possible experimental setup involving polarized goggles and filter. During the experiment, the subject wears a pair of polarizing goggles while the light coming from the projector is polarized through a filter. If the two polarizing devices (filter and goggles) polarize light in orthogonal planes, no light reaches the eye (i.e. right eye). This does not happen if the planes are parallel (i.e. left eye) and all light reaching the goggles passes through. For intermediate angles between the polarizing planes, various amounts of light reach the eye (not shown).