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Assumption: Cell-phones generate some degree of electro-magnetic radiation. Whether it's harmful or not is not the question here.

Claim: Certain devices may "neutralize" this radiation. (Ex: http://www.giawellness.com/2/products/terra-gia/cell-guard/)

Questions:

  • Is such a claim even physically possible with what is known today (in stick-on form, as advertized)?
  • Presumably a full case made out of special material could limit it.. What effect would a suitable case have on the call quality and/or wifi connectivity?

(Related Question: Could cell-phone radiation cause cancer?)

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  • $\begingroup$ Before you ask, nope, not planning on buying anything. Just curious. $\endgroup$
    – emragins
    Commented Mar 19, 2014 at 4:02
  • $\begingroup$ Your phone has to communicate with the cell towers... Turn off your phone or use it as intended. $\endgroup$
    – Brandon Enright
    Commented Mar 19, 2014 at 5:22
  • $\begingroup$ The "Cell Guard" product you link to can't work. It seems like their website is carefully worded so that their only claims are about how you feel, not about how it blocks EM radiation. The placebo effect is real. $\endgroup$
    – Brandon Enright
    Commented Mar 19, 2014 at 5:26
  • $\begingroup$ @BrandonEnright Totally! There's a number of pages out there such as "rifoffreport" and the like about them and similar products... Unfortunately, the scam reports seem to only allude or presume themselves about real-world science, so I decided to ask someplace grounded in facts and essentially internet-peer-reviewed. I trust y'all to actually know what you're talking about. :) $\endgroup$
    – emragins
    Commented Mar 19, 2014 at 5:49
  • $\begingroup$ To be sure, the cell-phone must generate electro-magnetic radiation during transmit as any radio must do to communicate with another radio: "Radio is the wireless transmission of signals through free space by electromagnetic radiation" en.wikipedia.org/wiki/Radio Thus, any device that genuinely 'neutralized' this radiation would prevent your cell-phone from transmitting to any cell tower and thus, making or receiving calls. $\endgroup$
    – Alfred Centauri
    Commented Mar 19, 2014 at 11:24

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A small attachment? No, not possible.

Think of it this way: If EM waves are emitted from the phone's antenna at point A, the only way they can be stopped from reaching point B is if either

  1. You place something directly between A and B that absorbs or reflects them, or
  2. You create an equal but opposite wave at B from somewhere else, destructively interfering with the signal from A so that there is no EM wave at B.

An attachment like the one linked can't shield all directions simultaneously, so option (1) doesn't work in general. With option (2), at best you can neutralize the wave at one point, but you can't generally neutralize it elsewhere at the same time. For the exact same reason there are noise cancelling headphones (neutralize sound at your eardrum) but not noise-cancelling devices fields that can make a whole airplane go silent. Something that makes destructive interference at one point will make constructive interference nearby.

Of course if you want to block EM waves, that's easy and you can do it for cheap. Surround your phone in metal (it can even have holes in it), creating a Faraday cage. It should be noted that shielding of EM waves also makes the phone not work - phones aren't magic, and that "radiation" is what they use to communicate. Block it and of course they stop working. If you want to see this effect on a large scale, just walk inside an earthquake-proof building that has lots of rebar (and doesn't have fancy cellular repeaters) - you'll see your signal strength die pretty rapidly.

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  • $\begingroup$ "rebar" is steel reinforcing embedded in concrete, right? (have never come across this word). +1BTW $\endgroup$
    – Selene Routley
    Commented Mar 19, 2014 at 7:21
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    $\begingroup$ Yep - I figure as long as the spacing is < ~1 ft. it will be a good Faraday cage for ~1 GHz signals, so it seems reasonable. Anecdotally, my phone never worked well indoors in California, even when reception was great outside. $\endgroup$
    – user10851
    Commented Mar 19, 2014 at 7:25

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