metal and EM waves

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metal and EM waves

Postby zetreque on November 20th, 2017, 12:36 am 

I am wondering if aluminum foil will reflect EM waves. I know they can block it. I just tested it myself by covering my cellphone with one layer of aluminum foil and I could not call it. What I don't know and can't test because I don't have a meter is if the EM is reflected (either grounded or not grounded).

Like if you have something transmitting EM waves and you send them at an aluminum foil (either grounded or not), will the foil in theory reflect the waves and you get 2x the amount or does it just absorb the waves?

According to this video it sounds like it is reflected.
https://www.youtube.com/watch?v=tJhbf-wDft0
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Re: metal and EM waves

Postby zetreque on November 20th, 2017, 1:04 am 

Oh, I forgot to mention that I know aluminum foil reflects IR, but I am curious about other parts of the spectrum such as what cellphones operate on.
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Re: metal and EM waves

Postby BurtJordaan on November 20th, 2017, 12:13 pm 

I think it is some of both absorption and reflection, but I don't know the percentages. It is very hard to stop metal surfaces reflecting EM waves - ask the air force. The reflection depends on the properties and the geometry of the metal surface and the relation of wavelength relative to the geometry.
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Re: metal and EM waves

Postby Braininvat on November 20th, 2017, 1:16 pm 

If your geometry is a parabola, and you put the cellphone at the focus, you would definitely have some signal boost if you needed it.
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Re: metal and EM waves

Postby zetreque on November 20th, 2017, 1:49 pm 

Braininvat » Mon Nov 20, 2017 9:16 am wrote:If your geometry is a parabola, and you put the cellphone at the focus, you would definitely have some signal boost if you needed it.


What if it's a flat wall and you have say a wifi router on one end of the room and an aluminum foil wall on the other side of the room and you are standing in the center?
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Re: metal and EM waves

Postby Braininvat on November 20th, 2017, 4:48 pm 

Well any bounce can add strength to the signal. Think about how a large mirror will brighten a room.
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Re: metal and EM waves

Postby wolfhnd on November 20th, 2017, 6:25 pm 

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Re: metal and EM waves

Postby zetreque on November 20th, 2017, 11:27 pm 

Cool find wolfhnd. I heard about that when looking it up last night but didn't actually look at it.

I'm still curious about what wavelengths of the EM spectrum and strengths are reflected by aluminum foil. I'm afraid to look into the academic papers because it will be over my head and too specific for my question.
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