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I was looking at my microwave the other day and I thought that the metal mesh screen might be acting like a set of perpendicularly oriented polarizers. Other explanations I've heard on how this screen blocks out radiation seem to hinge on the wavelength of microwaves being large enough that the spacing of the mesh screen effectively looks like a solid screen to incoming microwaves. Is it accurate to think of the mesh screen like a set of polarizers? If not then could the metal mesh screen be replaced by a mesh of any arbitrary material and still block out radiation?

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  • $\begingroup$ Would you consider a brick wall as a set of polarizers for visible light? $\endgroup$ – probably_someone Jun 27 '17 at 23:42
  • $\begingroup$ No. So then does that mean that the mesh screen doesn't necessarily need to be metal? Would a wooden mesh work just as well, or a glass mesh? I thought they might be polarizers because they looked like polarizers, but is that just coincedental? $\endgroup$ – Phaidros Jun 27 '17 at 23:55
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    $\begingroup$ Precisely. A metal sheet without holes would work just as well, but then you wouldn't be able to see inside. $\endgroup$ – probably_someone Jun 28 '17 at 0:24
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    $\begingroup$ In order for a polarizer to work, the length of the grating (not the spacing between the slats, but the length of said slats) should be greater than the wavelength of the waves. The wavelength of microwaves in a microwave oven is roughly 12 cm. The openings in the mesh of a microwave are typically less than 1 cm on a side. So it is literally not possible for the mesh to act as a polarizer. $\endgroup$ – probably_someone Jun 28 '17 at 1:44
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    $\begingroup$ Well, you'd have to change the openings from squares to very thin rectangles, but yes, that could work. The downside, of course, is that now you're cooking the rest of your kitchen as well. $\endgroup$ – probably_someone Jun 28 '17 at 2:02

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