Why is there no signal on the mobile phone in the elevator?

Because the elevator is shielded from electromagnetic signals. The signal problem in the elevator is somewhat similar to this. The elevator can be regarded as a closed conductor cavity. Due to the influence of free charge, electromagnetic waves do not easily pass through the conductor. In the signal frequency band of mobile phone, the penetration distance of electromagnetic wave in conductor is very small, and the intensity decays quickly.

Therefore, it is difficult for the signal sent by the mobile phone to reach outside the elevator, and it is also difficult for the electromagnetic signal outside the elevator to reach the mobile phone.

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