Answer: The Faraday Cage
Faraday cages are a tightly woven, but rarely seen part of our modern world in all areas from research laboratories to television cabling to server rooms in hardened government institutions.
A Faraday The cage is simply a housing made of a conductive material that blocks external static and non-static electric fields. What does that mean for the layman? Everything that is in a properly designed Faraday cage is perfectly isolated from external electromagnetic radiation. You could, for a pretty dramatic example, stand in a Faraday cage in the top of the Empire State Building, and any lightning that hits the cage would cause the electrical charge in the conductive material of the cage to spread, causing the lightning to strike Inside of the cage will be broken off so that you remain completely intact (see the photo here for a smaller but equally dramatic example of a Faraday cage in action).
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Where do we find these Faraday Cages in daily use today? Faraday cages are integrated into all types of structures, wiring and even clothing. Hospital MRI rooms are designed to work as Faraday cages to reduce external interference and improve the quality of MRI scans. The coaxial cable is wrapped in a sheath-like Faraday cage to protect the cable core from external noise and prevent the leakage of RF signals. Linemen, working on electrical lines, wear full suits of conductive mesh that allow them to work on high-voltage power lines in full safety – the current flows through their bodies like water over a fish. Which RFID-blocking wallets do you see everywhere? You guessed it. Small Faraday cages tuned to block the frequencies used by RFID readers.
Picture by Antoine Taveneaux / Wikimedia.