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Are there any nice experiments using wireless LAN access points or routers or mobile phones to demonstrate physical features of electromagnetic fields, especially em-waves?

More precisely I am looking for experiments which use one of the devices above as the main tool and some materials that can be purchased at a reasonable cost from, say, a hardware store or electronic supply store only. I do not impose any restrictions on the cognitive level the experiments aim at; undergraduate level is fine as well as graduate level in em-theory.

Please use separate answers for different experiments.

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I don't understand why the question is closed. If you close this question you have to close many other questions as well. The question is definitely related to physics. If you want to be more precise it's a physics education question but not a popular natural science one. –  student Dec 14 '10 at 8:50
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Let me list some other open questions on this site that by @noldorin's criteria do not belong here: "Home experiments to derive the speed of light", "Why do lightbulbs continue to glow when turned off", "what are good mechanics experiments for 10 year olds". I could go on, but its easier to just take a look at the column on the right of this page :-) –  user346 Dec 14 '10 at 20:26
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xkcd.com/397 –  Kostya Dec 15 '10 at 8:08
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Some open questions on mathoverflow (which is according to the faq ONLY for research level questions) which probably should be closed by noldorin's criteria: mathoverflow.net/questions/8846/proofs-without-words, mathoverflow.net/questions/8609/favorite-popular-math-book, mathoverflow.net/questions/1714/best-online-math-videos, mathoverflow.net/questions/30156/demystifying-complex-numbers –  student Dec 15 '10 at 16:08
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I vote for reopen –  Frédéric Grosshans Dec 16 '10 at 11:20

5 Answers 5

You can construct a slotted waveguide antenna for a wifi router. I guess that you can construct 2 of them, a working one with the slots at the right points, were the microwave power is at its maximum, and one with the slots at the wrong point, with the slots shifted by $\lambda/2$ to be at the point where the microwave power it minimal. The fact that the good one works and the other don't can be seen as a way to check the wavelength of the wifi signal. Maybe the best obtion would be to build one with "sliding slots", in order to go from one situation to the other.

You probably can play similar tricks with other wavelength dependent antenna design.

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You could construct a Faraday cage and see that if you put a mobile phone inside you don't get any signal.

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Mapping EM Waves from Dipole Antennae

  1. Apparatus: a wireless adapter with movable antennae, an OS with a wireless signal strength indicator (XP shows the number of bars for instance - or you could write a program for it).

  2. Procedure: place apparatus at different locations w.r.t the wireless router and measure the signal intensity as a function of location and the orientation of the receiving antennae relative to the orientation of the emitting antennae (on the router).

  3. Analysis: From form of intensity function determine signal strenth loss as a function of distance and relative orientation between the two antennae. Repeat in different locations and environments - indoors, outdoors, etc.

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The question requested specifically common household tools. an OS hardly qualifies. –  Sklivvz Dec 13 '10 at 22:15
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A computer with Windows is not a common household item? Um ... at least on the planet Earth it is, last I checked. –  user346 Dec 13 '10 at 22:36
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Wait so I you gave me a downvote because you think a PC is not a "common household tool"? Puhleeeze ! –  user346 Dec 13 '10 at 22:46

Simplest thing coming to my mind -- wrapping your mobile (or anything that is able to receive a signal) in some aluminium foil (or in anything made of conductive material).

Then your reciever won't be able to receive the signal. "'Cause conductors block e.m. waves."

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Simple, yes, but not very interesting. –  David Z Dec 16 '10 at 21:40
    
A very neat smooth wrapping of Al-foil does a so-so job of blocking wavelength small than the physical dimension of wrapping (because it simply re-radiates the signal), however balling it up first to get crinkly foil with lots of substructure solves that problem nicely. –  dmckee Mar 21 '11 at 2:19

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