polarized lights are produced by: LCD displays, by scattering (eg: sky + sunlight), by reflection (brewster's law), bi-refringent crystals, using a polarizing filter
if a polarizing filter is out over an unpolarized light source, polarized light will be obtained
only the E-field components parallel to the "polarization axis" if the filter are transmitted
the component at to this axis is blocked
a second filter can be used as an analyzer.
the amount transmitted though the second filter depends on the angle between the filters' polarization angles. this is described by malus's law:
