Question

what is polarization???

Answer 1

Polarization generally refers to an aligning. Some examples In physics are spins, electromagnetic radiation fields or dipole moments. the dipole moment is most interesting. Most atoms are neutral in charge so the electric field should be zero however the charge distribution is often significantly non uniform in the sense that one side of atom or molecule in more positive compare to the opposite side. This small average separation of + and - charges produces an electric field that does not follow coulombs law and is not spherical symmetric. The field is characterized by a quantity called a dipole moment which is a vector quantity whose magnitude is equal to the net charge times the mean separation of the charges causing the electric field and it direction in from the negative to positive side. When placed in an electric field the + side points in the direction of the applied electric field. Note that the charges don't have to explicily by + and _ but merely less negative on one side compared to the other.
More interestingly an atom of molecule which has a normally symmetric distribution of charge has this distribution distorted by an applied electric field so that a dipole moment is created. The dipole field lateral to the moment is in a direction to oppose the applied field thus reducing it. This property is responsible for insulation characteristics of plastic,s rubber or ceramics.

In the case of EM rad. polarization refers to the aligning of the E field in a certain direction. Usually, not always, EM rad is created with it E fields pointing in all directions perpendicular to the direction of propagation. The same applied to spins of nuclei atom or molecules although the spins themselves may be stationary the preferentially point in a certain direction.