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Empirically, we know that a mesh screen to block EM waves, must have mesh size much smaller than the wavelength. e.g. microwave oven

What I find perplexing, intuitively, is the geometry underlying this heuristic. The wavelength is defined in the z direction (Poynting vector of motion). But the mesh plane is the x,y plane, perpendicular to velocity.

How to reconcile this discrepancy?

Qmechanic
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Rich D
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1 Answers1

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What's hinted at in hyportnex's comment, is that while the wavelength is indeed varying along the direction of propagation, you need to remember that the physical interaction is between the field and the electrons in the metal.

So, what matters is the field, which is perpendicular to the Poynting vector here and parallel to the mesh in your thought experiment.

KAHR-Alpha
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