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Despite water being a conductor how does light pass through water.[note: electric field inside a conductor is zero due to gauss' law]

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  • $\begingroup$ 1. What has the picture to do with the question? 2. Why is this tagged wave-particle-duality? $\endgroup$ – ACuriousMind Nov 2 '17 at 12:37
  • $\begingroup$ Why is water clear? $\endgroup$ – ldgorman Nov 2 '17 at 12:46
  • $\begingroup$ @ACuriousMind regarding the graph " BarsMonster's excellent graph shows us where in the spectrum water's internal mechanics tends to absorb photons for good (thus where it is opaque) " $\endgroup$ – ldgorman Nov 2 '17 at 12:58
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    $\begingroup$ Ultimately, to answer your question, a light wave is not described by electrostatics. $\endgroup$ – ldgorman Nov 2 '17 at 13:03
  • $\begingroup$ Yes, it's not that the e field is zero, but that mobile charges in the conductor rearrange to keep it zero. This takes some time. $\endgroup$ – JMLCarter Nov 2 '17 at 13:10
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To expand on the comments, your question includes two false assumptions:

1- The electric field in a conductor is zero in electrostatics only. There are non-zero electric field in conductors all the time. For example, to get a steady current in a medium, even a conducting wire, you need an electric field.

2- Water itself is not a very good conductor. Adding ions in the water will increase its conductivity significantly.

Ions in water are much less mobile than electrons in a metal. To have an effect on EM wave propagation, the charges in a material must be able to rearrange quickly enough to affect the propagating electromagnetic wave. The ions in water are too heavy and too much impeded by the surrounding water to do so for light. However, for longer wavelengths, water with dissolved ions is indeed opaque. That is why submarines cannot communicate using radio waves when submerged (only broadly speaking, they can if very close to the surface or if using extremely long wavelengths a bit deeper)

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