Vacuum is said to have an intrinsic impedance. What is the source of this? Impedance is quite understandable in bulk matter, but I'm unable to comprehend it's presence in vacuum.
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Possible duplicates: https://physics.stackexchange.com/q/79364/2451 , https://physics.stackexchange.com/q/36448/2451 and links therein. – Qmechanic Jun 29 '20 at 10:49
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Impedance is a response of material to excitation. E.g., if we define an impedance of a conductor as a ratio of the applied bias to the resulting current, $$Z(\omega) =\frac{V(\omega)}{I(\omega)},$$ then nothing prevents us from defining it in the same way for vacuum. Naturally one would expect this impedance to be something simple like 1 (electromagnetic field passes without attenuation) or 0 (no electric current).
Specifically, one talking about the impedance of free space one often talks about the propagation of electromagnetic field $$Z = \frac{E}{H} = \sqrt{\frac{\mu_0}{\epsilon_0}},$$ which has dimensionality of resistance. The fact that in SI system of units this ratio is not $1$ is one of the main arguments against using this system of units in physics.
Roger V.
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@hyportnex thanks, I corrected the formula. However, I do not use the SI units: $\mu_0 = \epsilon_0 = 1$ – Roger V. Jun 29 '20 at 12:47
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your voltmeter must be calibrated in statvolts, how is your car battery? – hyportnex Jun 29 '20 at 12:55
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Can you try to figure out how to do the maths mark-up? It would make it easier to read... – Oscar Bravo Jun 29 '20 at 13:01
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@OscarBravo what exactly the problem? If you want to edit something for better readibility - feel free to do so. – Roger V. Jun 29 '20 at 13:03
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@hyportnex I suppose that engineers find SI units more convenient - I am a theoretical physicist. – Roger V. Jun 29 '20 at 13:05
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@Vadim Do you see the mathjax correctly formatted? I see the mark-up... It's not just you, it's the whole site - that's weird... – Oscar Bravo Jun 30 '20 at 09:13
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