Terminology
The analogous quantity for a plane wave travelling through a dielectric medium is called the intrinsic impedance of the medium, and designated η (eta). Hence Z0 is sometimes referred to as the intrinsic impedance of free space, and given the symbol η0. It has numerous other synonyms, including:
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- wave impedance of free space,
- the vacuum impedance,
- intrinsic impedance of vacuum,
- characteristic impedance of vacuum,
- wave resistance of free space.
Read more about this topic: Impedance Of Free Space