What is "circular polarization"

Circular \Cir"cu*lar\, a. [L. circularis, fr. circulus circle: cf. F. circulaire. See Circle.]

1. In the form of, or bounded by, a circle; round.

2. repeating itself; ending in itself; reverting to the point of beginning; hence, illogical; inconclusive; as, circular reasoning.

3. Adhering to a fixed circle of legends; cyclic; hence, mean; inferior. See Cyclic poets, under Cyclic.

   Had Virgil been a circular poet, and closely adhered to history, how could the Romans have had Dido?
   --Dennis.

4. Addressed to a circle, or to a number of persons having a common interest; circulated, or intended for circulation; as, a circular letter.

   A proclamation of Henry III., . . . doubtless circular throughout England.
   --Hallam.

5. Perfect; complete. [Obs.] A man so absolute and circular In all those wished-for rarities that may take A virgin captive. --Massinger. Circular are, any portion of the circumference of a circle. Circular cubics (Math.), curves of the third order which are imagined to pass through the two circular points at infinity. Circular functions. (Math.) See under Function. Circular instruments, mathematical instruments employed for measuring angles, in which the graduation extends round the whole circumference of a circle, or 360[deg]. Circular lines, straight lines pertaining to the circle, as sines, tangents, secants, etc. Circular note or Circular letter.

   1. (Com.) See under Credit.

   2. (Diplomacy) A letter addressed in identical terms to a number of persons.

      Circular numbers (Arith.), those whose powers terminate in the same digits as the roots themselves; as 5 and 6, whose squares are 25 and 3

6. 
   --Bailey.
   --Barlow.

   Circular points at infinity (Geom.), two imaginary points at infinite distance through which every circle in the plane is, in the theory of curves, imagined to pass.

   Circular polarization. (Min.) See under Polarization.

   Circular sailing or Globular sailing (Naut.), the method of sailing by the arc of a great circle.

   Circular saw. See under Saw.

In electrodynamics, circular polarization of an electromagnetic wave is a polarization in which the electric field of the passing wave does not change strength but only changes direction in a rotary manner.

In electrodynamics the strength and direction of an electric field is defined by what is called an electric field vector. In the case of a circularly polarized wave, as seen in the accompanying animation, the tip of the electric field vector, at a given point in space, describes a circle as time progresses. If the wave is frozen in time, the electric field vector of the wave describes a helix along the direction of propagation.

Circular polarization is a limiting case of the more general condition of elliptical polarization. The other special case is the easier-to-understand linear polarization.

The phenomenon of polarization arises as a consequence of the fact that light behaves as a two-dimensional transverse wave.