- Polarizer is a device which transmits only the component of polariztion parallel to
its transmission axis. By using a polarizer, the plane of a plane-polarized
wave can be changed; a circularly polarized or unpolarized light can be
changed to plane-polarized.
- When a circularly or unpolarized wave (natural light) is incident on a polarizer of whatever
the orientation of transmission axis, the wave intensity passing through
is always one-half of the incident one (after averaging over many random
changes in the case of unpolarized wave).
- No light can pass through two polarizers whose transmission axes are crossed perpendicularly.
However, when a third polarizer is inserted between them with an angle not
parallel to either of them, some light can finally pass through.