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I read that steel/iron/metal/conducting cages, with gaps less than the wavelength of electro magnetic waves, shield whatever is inside from that radiation. But when I put my mobile inside a cooker and called it, it rang. Why isn't this working? Please explain Faraday cage working more in detail.

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  • \$\begingroup\$ Do you have a window in your cooker? Are you fairly close to a cell antenna? Nothing attenuates perfectly. \$\endgroup\$ – Andy aka Jul 4 at 12:41
  • \$\begingroup\$ @Andyaka I put the router inside the cooker and yet I'm getting a WiFi signal. This is the main problem. \$\endgroup\$ – Vishwa Mithra Tatta Jul 4 at 12:43
  • \$\begingroup\$ Is the cooker fully covered by metal ?. some times there are non metallic bushings or gaskets where the lid meets the rest of the cooker. \$\endgroup\$ – AJN Jul 4 at 12:48
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    \$\begingroup\$ @user163416 How did you power the router when it was inside the cooker? there would have been a gap in the lid where the power cord entered the cooker. A few centimetres in any direction is enough. Any hole bigger than the holes in a microwave oven door's mesh can allow microwave signals to pass through. \$\endgroup\$ – AJN Jul 4 at 12:51
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    \$\begingroup\$ "Cooker" means different things in different parts of the world. You have no location information in your question or user profile so we don't know what you mean by the word. Please edit to clarify. A photo would help and you should try to clarify the points raised in the comments above. Also your question talks about a phone and your comments about a WiFi router. Please be clear. \$\endgroup\$ – Transistor Jul 4 at 13:00
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To be a good Faraday cage, an enclosure needs to be completely sealed, with no gaps larger than about a tenth of the wavelength of the radio waves you want to keep out.

Microwave ovens have a tightly-fitting door, and a metal mesh in the door where the window is. But even they won't completely block a mobile phone signal.

A normal domestic oven may have a glass window, which would let the radio waves in. Even without a window, they have loosely fitting doors with rubber seals, and rubber won't block a radio signal.

See also This Physics Stack Exchange question.

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  • \$\begingroup\$ Modern microwave ovens do not have a tight-fitting door, they have a \$\lambda\$/4 gap which is tuned to attenuate the magnetron frequency and a microwave absorbing material. So the attenuation at other frequencies may not be all that great. \$\endgroup\$ – Spehro Pefhany Jul 4 at 14:28

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