The stack of eight plates transmits about 64% of the incident intensity; 56% of that which is transmitted is linearly polarized and vibrates on the plane of incidence and the remaining 44% is not polarized. Therefore, when the analyser, oriented with the axis of transmission perpendicular to the plane of incidence, receives the beam transmitted by the stack of plates with Brewster incidence, it absorbs 78% of the intensity and transmits the remaining 22% and on the screen we observe a minimum of illumination. By orienting the analyser with the axis of transmission perpendicular to the plane of incidence of the beam of natural light onto the stack of plates and by varying the inclination of the latter, it is possible to determine the position at which the intensity transmitted by the analyser is minimum and thus verify Brewster's law. Verification can be repeated with greater precision by using the stack as a polarizer by reflection; it is sufficient to orient the analyser with the axis of transmission parallel to the plane of incidence and, by varying only the inclination of the stack, find the one at which the intensity transmitted by the analyser is minimum.
The apparatus also makes it possible to verify Biot's experiments on crystal optical activity by using plates of quartz, laevorotatory and dextrorotatory, sliced perpendicularly to the optical axis.
It is also possible to observe the chromatic polarization figures produced by crystalline plates sliced with different inclinations with respect to the optical axis or by plates of tempered glass.
It is clear that if the stack had a sufficiently high number of plates (25÷30), the beam transmitted, as was verified by Malus, would be totally polarized and the measurements made in transmitted light would have the same precision as those made in reflected light.