A system of three polarizers P₁, P₂, P₃ is set up such that the pass axis of P₃ is crossed with respect to that of P₁.
The pass axis of P₂ is inclined at 60^o to the pass axis of P₃. When a beam of unpolarized light of intensity I0 is
incident on P₁, the intensity of light transmitted by the three polarizers is I. The ratio () equals (nearly) :