Thus, if an unpolarised light wave is incident on such a polaroid then
the light wave will get linearly polarised with the electric vector oscillating
along a direction perpendicular to the aligned molecules; this direction
is known as the pass-axis of the polaroid Thus, if the light from an ordinary source (like a sodium lamp) passes
through a polaroid sheet P1, it is observed that its intensity is reduced by
half Rotating P1 has no effect on the transmitted beam and transmitted
intensity remains constant Now, let an identical piece of polaroid P2 be
placed before P1