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prateek
science forum beginner

Joined: 24 Jun 2006
Posts: 1

Posted: Sat Jun 24, 2006 7:03 pm    Post subject: Skin Depth in metals

As i understand, EM waves do not penetrate the metals. Only a small
portion of the energy is absorbed depending on the skin depth and rest
is all reflected.So how do the antennas, which are all metallic, absorb
the wave power?

prateek
Dave
science forum Guru Wannabe

Joined: 23 Apr 2005
Posts: 191

Posted: Sun Jun 25, 2006 1:35 am    Post subject: Re: Skin Depth in metals

they don't absorb it, the fields cause the electrons in the metal to move
which induces currents in the metal.

"prateek" <prateekprashar2003@yahoo.co.in> wrote in message
 Quote: As i understand, EM waves do not penetrate the metals. Only a small portion of the energy is absorbed depending on the skin depth and rest is all reflected.So how do the antennas, which are all metallic, absorb the wave power? prateek
noshellswill
science forum beginner

Joined: 15 Apr 2006
Posts: 12

Posted: Mon Jun 26, 2006 5:46 am    Post subject: Re: Skin Depth in metals

On Sat, 24 Jun 2006 12:03:52 -0700, prateek wrote:

 Quote: As i understand, EM waves do not penetrate the metals. Only a small portion of the energy is absorbed depending on the skin depth and rest is all reflected.So how do the antennas, which are all metallic, absorb the wave power? prateek

BigP:

At the receiver-antenna surface, the tangential-component of H-field is
discontinuous , and proportional to an induced surface current_density ...
say J = J0*cos< w*t > ..... etcetc.

nss
****************
Timo Nieminen
science forum Guru Wannabe

Joined: 12 May 2005
Posts: 244

Posted: Mon Jun 26, 2006 11:39 am    Post subject: Re: Skin Depth in metals

On Sun, 24 Jun 2006, prateek wrote:

 Quote: As i understand, EM waves do not penetrate the metals. Only a small portion of the energy is absorbed depending on the skin depth and rest is all reflected.So how do the antennas, which are all metallic, absorb the wave power?

As others have written, antennas don't work by absorption. Also, you might
want to compare the skin depth with the typical thickness of antennas.

The antenna doesn't absorb (or at least, that isn't why it works), the
circuit attached to the antenna absorbs. The antenna converts radiation in
free space into guided waves going into the rest of the circuit.

--
E-prints: http://eprint.uq.edu.au/view/person/Nieminen,_Timo_A..html
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html

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