Explain the polarization of light by a thin plastic-like sheet.

(N/A) The phenomenon of obtaining plane-polarized light from unpolarized light is called polarization.
$A$ sheet that can produce polarized light from unpolarized light is called a polaroid.
Examples include thin plastic sheets and tourmaline plates.
$A$ polaroid consists of long-chain molecules aligned in a specific direction.
Electric field vectors oscillating along the direction of the aligned molecules are absorbed,while components oscillating in the perpendicular direction pass through. This perpendicular direction is called the pass axis of the polaroid. It allows components of light vectors parallel to the pass axis to pass through,while perpendicular components are absorbed. Consequently,the waves that emerge are linearly plane-polarized.
If light from an ordinary source passes through a single polaroid sheet $P_{1}$,its intensity is reduced by half. Rotating $P_{1}$ has no effect on the transmitted beam,and the transmitted intensity remains constant.
Now,let an identical piece of polaroid $P_{2}$ be placed before $P_{1}$. Rotating $P_{1}$ now causes the intensity of light emerging from $P_{1}$ to vary.
When the pass axes of $P_{2}$ and $P_{1}$ are parallel,the light vectors passing from $P_{2}$ also pass through $P_{1}$,resulting in maximum transmitted intensity.
When the $P_{1}$ sheet is rotated by $90^{\circ}$ relative to $P_{2}$,the intensity of light emerging from $P_{1}$ becomes zero. This is illustrated in the figure.