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[SOLVED] If air is an insulator how do radio waves, cell phone signals and WiFi travel?

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unbuildpain

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If air is an insulator how do radio waves, cell phone signals and WiFi travel?
 

BradtheRad

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radio waves, cell phone signals and WiFi
These particular types travel as photons (aka electromagnetic waves). Air is not necessary.

For a while it was theorized that some invisible medium (popularly named 'ether') was needed as a means for the invisible radio waves to travel. Today ether is more of a poetic term in regard to radio.
Neverthelesss even today we don't understand exactly what photons are. In some ways they are like particles, and in some ways like waves. It's true photons (electromagnetic waves) are influenced by kinks and bends in the space-time continuum in their travels. Thus we might find the idea of an 'ether' medium continues to apply in some hard-to-define sense.
 
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unbuildpain

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I thought photons referred to only light particles/waves.

Shouldn't electromagnetic waves be stopped in an insulator? Because they don't have any conductivity to move.
 

FvM

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Don't need to refer to photons. Just coupled electrical and magnetical fields as described in the Maxwell equations. Air and vacuum has relative permittivity around 1, sufficient to carry AC currents.
 

unbuildpain

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Don't need to refer to photons. Just coupled electrical and magnetical fields as described in the Maxwell equations. Air and vacuum has relative permittivity around 1, sufficient to carry AC currents.
So air isn't a pure insulator?
 

FvM

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The question isn't specifically about air, electromagnetic waves also travel through empty space.
 

betwixt

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Presumably you think satellite communications cannot work and Sunlight only exists in everyone's imagination, they all pass radiation through vacuum too.

Brian.
 

unbuildpain

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Presumably you think satellite communications cannot work and Sunlight only exists in everyone's imagination, they all pass radiation through vacuum too.

Brian.
If you can't explain how, why do you make these kinds of comments? They lower the quality of the forum.
 

betwixt

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I disagree. You implied that air is a necessary medium for radio waves to travel through and I pointed out that many of the things we take for granted such a long range radio communication and even solar radiation can travel through vacuum with no difficulty. You were confusing sound with electromagnetic waves. Sound is produced by compressing air and travels as the compression wave influences adjacent air molecules, EM waves work quite differently and so not require a compressible medium to propagate through.

Brian.
 

unbuildpain

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I didn't have any confusion between mechanical waves(sound waves) and electromagnetic waves(radio, cell phone and WiFi).

Aren't electromagnetic waves made up of electrons? Electrons need conductive material to move, air is mentioned in textbooks as an insulator, so I'm confused how they can move in air.
 

wwfeldman

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air is an insulator - but not a very good insulator
this shows up, in part, via snell's law
the index of refraction is n = c/v(medium)
which in vacuum is c/c, or 1 (exactly)
the index of refraction of air is (about) 1.0004, hence, for most purposes
we can treat air as the same as vacuum

electromagnetic waves do not consist of electrons

EM waves are waves of time varying and space varying electric and magnetic fields
per Faraday and Maxwell, changing electric fields induce magnetic fields,
and changing magnetic fields induce electric fields, hence EM waves are self propagating
(that is, they re-induce themselves continuously)

EM waves include, but are not limited to, gamma through radio, as in the chart.
visible light is that short portion that we see as colors.
there is no reason to believe the chart stops at either end.
the chart shows the limit of our ability to observe and produce EM waves.

1596458438689.png

also, electrons (and hence current) do not need a medium to travel through
there are a variety of particle accelerators (cyclotrons, synchronous, etc) that
accelerate all manner of particles in a vacuum.
these also occur naturally, such as the solar wind and cosmic rays (muons, etc)
 

unbuildpain

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air is an insulator - but not a very good insulator
this shows up, in part, via snell's law
the index of refraction is n = c/v(medium)
which in vacuum is c/c, or 1 (exactly)
the index of refraction of air is (about) 1.0004, hence, for most purposes
we can treat air as the same as vacuum

electromagnetic waves do not consist of electrons

EM waves are waves of time varying and space varying electric and magnetic fields
per Faraday and Maxwell, changing electric fields induce magnetic fields,
and changing magnetic fields induce electric fields, hence EM waves are self propagating
(that is, they re-induce themselves continuously)
How do Faraday cages block electromagnetic waves then?

EM waves include, but are not limited to, gamma through radio, as in the chart.
visible light is that short portion that we see as colors.
there is no reason to believe the chart stops at either end.
the chart shows the limit of our ability to observe and produce EM waves.
You mean to say there is more after gamma rays? And thus far we have only been able to identify upto gamma rays?

also, electrons (and hence current) do not need a medium to travel through
there are a variety of particle accelerators (cyclotrons, synchronous, etc) that
accelerate all manner of particles in a vacuum.
these also occur naturally, such as the solar wind and cosmic rays (muons, etc)
Why are wires needed for electricity to pass through? Can there be wireless electricity?
 

wwfeldman

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Faraday Cage:

gamma rays
we call them gamma rays - they are high energy electromagnet waves
you can only detect what you have an instrument to detect

wireless electricity is called lightning
but lightning is an effect of a static discharge, rather than a continuous current
for example, you can turn on a fan, and leave it on
electricity keeps the fan going continuously and it can be plugged in the wall, or run on batteries
in either case, the fan runs until we turn it off, or until the power source "dies"
 

schmitt trigger

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BradtheRad

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Radio waves are known to bounce off the ionosphere (a high altitude layer of earth's atmosphere), and in that sense they don't get past it. Yet that is not due to air being an insulator, but is a different phenomenon.

-------------------------------------------------------

I thought photons referred to only light particles/waves.

Shouldn't electromagnetic waves be stopped in an insulator? Because they don't have any conductivity to move.
Light and radio are of the same nature as residing on the electromagnetic spectrum. If light is photons then so is radio.

Magnetic is not the same as electromagnetic, although electricity is related to both and can be involved in conversion one to the other. Thus radio waves are not identical to magnetism. Radio waves travel as photons do, continuing in a given direction, and they travel light years across the universe.

However a magnetic field does not travel across the universe, nor is a magnetic field directional in the same sense that photons are.

----------------------------------------------------------

Aren't electromagnetic waves made up of electrons? Electrons need conductive material to move, air is mentioned in textbooks as an insulator, so I'm confused how they can move in air.
We might guess that an electron is knocked out of orbit around an atom and flies off as a photon at the speed of light. This surmise may not necessarily be correct, however.

Current electricity is electrons moving through wire by traveling from atom to atom. The speed of any one electron is reported as several inches per second. However the electrical charge itself moves through wire at the speed of light.
 

c_mitra

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First of all, you need to understand the concept of field.

A charge placed at a point produces an electric field. Same is true for a magnetic pole or a mass can produce a gravitational field.

These are force fields; an electric field can exert a force on another electric charge placed within its reach.

These fields can exist in a vacuum. These fields do not need a medium to exist. This is very important to understand. Force can be exerted without a medium, at a distance.

Now consider one charge is moving (say like a pendulum in a simple harmonic motion). At any distant point the electric field will also be changing because the field strength is dependent on the distance. The motion of the charge produces a current. And a current is associated with a magnetic field. So the changing electric field at a distance from the oscillating charge is associated with a changing magnetic field also. These will have the same frequency as the frequency of the oscillating charge. And an electromagnetic wave is born!

Second, you need to understand the concept of vacuum. We usually understand vacuum as space devoid of matter. But how about energy?

When you have a force field (produced by a charge at a distance), the force field is associated with some potential. Thus the empty space is associated with some energy (energy density). This energy density is associated with a temperature. Thus empty space can have a temperature. And this temperature can be small, very low, but not zero. Also remember that energy has some association with mass. So we can have space devoid of matter but not devoid of energy.

How the electromagnetic wave travels? it is simple but can be confusing.
 
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