[kuhsaft]

> Do tell because as far as I'm aware Maxwell's equations don't have an asterisk on them that say "doesn't work below 1 GHz".

Did you really just pull out Maxwell's equations?

EM interacts with matter in different ways. Glass hardly attenuates visible light, but wood does. 2.4 Ghz can pass through walls better than 5Ghz.

There's the concept of permittivity wherein Maxwell's equations are defined in free space with vacuum permittivity.

https://en.wikipedia.org/wiki/Vacuum_permittivity#Permittivi...

To accurately model EM waves, you need more than just Maxwell's equations. You require material equations to model interactions of EM with media.

If you want to get really advanced, whereas Maxwell's equations are classical physics, there's Quantum electrodynamics (QED) which can model interactions of EM and matter.

https://en.wikipedia.org/wiki/Quantum_electrodynamics

[almostgotcaught]

> There's the concept of permittivity

> You require material equations to model interactions of EM with media

> Quantum electrodynamics (QED) which can model interactions of EM and matter.

It's amazing how condescending some people on here are; how could you possibly have missed literally in the first sentence of my response

> ... my physics degree

[kuhsaft]

> It's amazing how condescending some people on here are

You literally started your comment with "Lol news to me", then you used your degree as if it made you more knowledgeable than anyone else here. Take a look in the mirror?

> ... Do tell

I did?

The extra information isn't to condescend. It's for other people that want to know more about the science.

[asdefghyk]

RE "....Glass hardly attenuates visible light...." Clear glass blocks about 5% visible light

[kuhsaft]

Depends on the frequency of EM. Fiber optic communications use specific frequencies to minimize attenuation in cables.

https://en.wikipedia.org/wiki/Optical_fiber#Mechanisms_of_at...

Same with communications over coax. Obviously visible light doesn't transmit well over copper, but a spectrum of radio waves do, some better than others.

[Sesse__]

Fiber optics also uses _exceptionally_ clear glass.

If the ocean were as clear as your average long-distance fiber cable, you would see down to the bottom of the Mariana Trench (also in the range of visible light, AFAIK).

[kuhsaft]

> Fiber optics also uses _exceptionally_ clear glass.

Clear in certain wavelengths. Depends on the composition of the glass.

https://en.wikipedia.org/wiki/Optical_fiber#/media/File:Si_Z...

Silica glass behaves differently from ZBLAN (fluorozirconate glass).

Which goes to show how complicated EM interactions with media can be. It's generally easier to just empirically measure attenuation through some medium and use the empirical measurements as a model.

[Sesse__]

It's exceptionally clear compared to e.g. window glass even in the visible spectrum of light. You can shine a red light source into a 10 kilometer standard G.657 fiber (optimized for 1310/1550nm, i.e. deep infrared) and it will still be visible just fine on the other end. If you did that with regular glass, it would hardly go ten meters.

[schoen]

What are the relative contributions of the total internal reflection property of the fiber optic cable and the particular low-attenuation material it's made of?

[kuhsaft]

Oh yeah. I'm not saying otherwise. Someone replied "Clear glass blocks about 5% visible light". I guess "clear glass" is pretty subjective. At what level of attenuation would someone consider glass not clear? xD