The impedance of free space, Z0, is a physical constant relating the magnitudes of the electric and magnetic fields of electromagnetic radiation travelling through free space. That is, Z0 = |E|/|H|, where |E| is the electric field strength and |H| magnetic field strength. It has an exact value, given approximately as 376.73031... ohms.
The impedance of free space equals the product of the vacuum permeability or magnetic constant μ0 and the speed of light in vacuum c0. Since the numerical values of the magnetic constant and of the speed of light are fixed by the definitions of the ampere and the metre respectively, the exact value of the impedance of free space is likewise fixed by definition and is not subject to experimental error.
Read more about Impedance Of Free Space: Terminology, Relation To Other Constants, Exact Value, 120π-approximation
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