Impedance of free space

Physical constant; ratio of electric to magnetic field strength in a vacuum

In electromagnetism, 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, Z 0 = | E | | H | , {\displaystyle Z_{0}={\frac {|\mathbf {E} |}{|\mathbf {H} |}},} where |E| is the electric field strength, and |H| is the magnetic field strength. Its presently accepted value is Z0 = 376.730313412(59) Ω, where Ω is the ohm, the SI unit of electrical resistance.

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