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I would like to demonstrate to my students the effect of electromagnetic shielding by a Faraday cage. I tried two arrangements of cages. One was an inverted metal utensil holder having holes about 1 cm in diameter, which I placed on top of aluminum foil to get metal on all sides. The other arrangement was simply an aluminum pie plate inverted on top of another plate. With both arrangements, I put a cell phone in the "cage" and called the number. I was surprised that the phone still received the signal. Can you please explain possible reasons why my arrangements did not effectively shield the cell phone from the signal? Thank you!
Question Date: 2006-06-29
Answer 1:

My guess is that it has something to do with the wavelength of the radio light that your cell phone is receiving being much longer than the thickness of the metal. It may be exciting the electrons, but there may not be enough distance to absorb the waves as there would be with higher frequency light, in much the same way that you need an antenna to collect the light in the first place.

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