So this isn’t the most quantitative I don’t the physics enough to say that it will withstand an EMP. Does magnitude of EM matter?
But you can stick a small AM/FM radio in with the volume up. And when you close the tin it will go silent.
Discussion
lol this was not proof read well. But I hope you get my meaning. You can “prove” it’s a faraday cage by blocking the signal to a radio, probably a phone too.