ELI5: How are microwaves kept inside microwave ovens?
Posted Mar 18, 2017, 2:50 PM UTC
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Electricity travels along the surface of metal objects, but not through the center. Metal also will block radio signals from passing though, and all a radio signal is is electromagnetic radiation similar to a microwave. Much of the microwave is metal plated aside from the door. Microwaves have a specific set of wavelength. These can range anywhere from 10cm to 0.1cm. If you look at a microwave door, you'll see what looks like a grid of wires. This is actually called a faraday cage and the spacing between the wires acts as a kind of net, catching the microwaves so they can't escape.
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The metal walls of the oven reflect the microwaves. The door also contains a metal mesh which reflects microwaves back into the centre of the oven.
I also heard that the mesh has holes too small for the waves to come through
That's right. The wavelength is over 122 mm or 4.8 inches. The door is opaque to 2450 MHz.
Well I certainly didn't know the wavelenght is that fucking big
And that's nowhere near the edge of the electromagnetic spectrum, most radio waves are metres long.
And opening the door of the oven triggers an immediate shutdown of the magnetron device that produces the microwaves.