What parameter can be used to distinguish between linear and circular polarization? Please also state its typical limit.

The parameter that can be used to distinguish between linear and circular polarization is the Ellipticity angle (η).

The ellipticity angle is the angle that the electric field vector of the electromagnetic wave describes in the plane perpendicular to the direction of propagation.

For linear polarization, the ellipticity angle is 0° or 180°. This is because the electric field vector describes a line in the plane perpendicular to the direction of propagation.

For circular polarization, the ellipticity angle is ±45°. This is because the electric field vector describes a circle in the plane perpendicular to the direction of propagation.

So, the typical limit to distinguish between linear and circular polarization is the ellipticity angle. If the ellipticity angle is 0° or 180°, the polarization is linear. If the ellipticity angle is ±45°, the polarization is circular.

The parameter that can be used to distinguish between linear and circular polarization is the Ellipticity angle (η).

The ellipticity angle is the angle that the electric field vector of the electromagnetic wave traces out in a plane perpendicular to the direction of propagation.

For linear polarization, the ellipticity angle is 0° or 180°. This is because the electric field vector traces out a line in the plane perpendicular to the direction of propagation.

For circular polarization, the ellipticity angle is ±45°. This is because the electric field vector traces out a circle in the plane perpendicular to the direction of propagation.

The typical limit for distinguishing between linear and circular polarization is when the ellipticity angle is neither 0° nor 180°, nor ±45°. In this case, the polarization is elliptical, which is a general form of polarization that includes both linear and circular as special cases.