Intrinsic impedance of a medium I am trying to understand what the intrinsic impedance of a medium means. I understand the mathematical definition of it, but it doesn't speak much about the concept to me.
What does intrinsic impedance mean conceptually? All I understand is that the electric field intensity is going to be much higher than the magnetic field intensity if the intrinsic impedance is high. Do conductors have higher or lower intrinsic impedance than lossless dielectric?
My guess is that at high frequency, conductors have high intrinsic impedance whereas lossless dielectrics have high intrinsic impedance at low frequency, and vise versa. Am I correct on this?
Also, why is the wave impedance called "impedance"? From what I know, it is merely a ratio between an electric field intensity and a magnetic field intensity. It says nothing about the material's ability to "impede" something. Is it a misnomer?
 A: For all practical purposes when a medium can sustain a TEM (transverse electromagnetic) wave then the wave impedance is the ratio of the corresponding electric and magnetic field components, that is $\mathcal Z_0 = \frac {E_x}{H_x}=\frac{E_y}{H_y}$ where I assume that wave front is in the $xy$ plane. In free space and using MKS SI units $\mathcal Z_0 = \sqrt{\frac{\mu_0}{\epsilon_0}}=120\pi [\rm{\Omega}] $. In linear material medium characterized by permittivity and permeability $\mathcal Z_m = \sqrt{\frac{\mu_r\mu_0}{\epsilon_r\epsilon_0}}$
The concept can be extended to a waveguide filled with a linear medium. For TEM wave to exist the waveguide must have at least two conductors and is important that the medium fill the guide completely and uniformly. The presence of metal will change the ratio $E/H$ from $\mathcal Z_m$ that is dependent on the medium only to something that represents the ratio of the inductance per unit length and capacitance per unit length within the medium.
 In general, one can define impedance parameters for other propagating waveguide modes, such as TE or TM. The corresponding impedances are related to the transmission line representation of the waveguide propagation; this has mostly theoretical use. Instead, one uses scattering matrix $\mathbf S$ with which if desired one can associate an impedance matrix $\mathbf Z= (\mathbf I +\mathbf S)(\mathbf I -\mathbf S)^{-1}$. Unlike impedance the scattering parameters *always* exist and finite, and one can measure them directly. In fact, at microwaves one always measures the scattering parameters and never that of impedance.
(Impedance means something that impedes, here current being impeded at a given voltage, but its historical origin have no import in practice.)
