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Polarization of Light

Light is an electromagnetic wave and propagates with a oscillating the electric field and the magnetic field perpendicularly to the propagation direction. This indicates that "light is a transverse wave" as shown in Figure 1.

Figure 1. the oscillation direction of the electric filed and the magnetic field of light

The polarized wave consists of the magnetic and electric fields that oscillate in only one direction. In case of Figure 1, this type of light is called "linearly polarized light" because the electric and magnetic field oscillate in a straight line direction. The direction of polarization is generally based on the oscillation direction of the electric field.
What kind of polarized light exists besides linearly polarized light? Here z axis is defined as the propagation direction, x and y axes are perpendicular to the z axis. The light propagates with the rotation of the electric and magnetic field in the x-y plane as shown in Figure 2. This type of light is called "circular polarization of light".

Figure 2. circular polarization of light

If the electric and magnetic filed oscillate on the oval in the x-y plane, the light called "elliptic polarizing". Furthermore, the polarized light perpendicular to an incident surface is called "p-polarized light". On the other hand, the polarized light parallel to an incident surface is called "s-polarized light" originated from "senkrecht (Germany)".
We return to the explanation for the linearly polarized light. Natural light (generally from Sun) is not polarized. In other wards, natural light includes numerical lights polarized in various directions. We generally use a deflection plate when we extract the polarized light in a specified direction from natural light. 　

Figure 3. Deflection plate

Figure 3 shows light into a deflection plate. This type of the deflection plate absorbs the propagating electric field except for it oscillate in the horizontal direction. Thus, the horizontally polarized light is only exist after passing through the deflection plate. This technique is widely applied for example lasers, sun glasses and so on.

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