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Microwave Reflectors

  1. Oct 10, 2005 #1
    Do materials exist which can efficiently reflect microwaves, radio waves and other long wavelength electromagnetic waves?
     
  2. jcsd
  3. Oct 10, 2005 #2

    Danger

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    Yes, hence the existence of parabolic antennae.
     
  4. Oct 10, 2005 #3
    Any metal will reflect radio and microwaves, but a highy polished metal like silver or gold would refelct microwaves better.
     
  5. Oct 10, 2005 #4
    But wouldn't the microwaves heat the metals up by inducing currents?
     
  6. Oct 13, 2005 #5

    Astronuc

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    As far as I know, the energy density in the microwaves or radar are very low, and so therefore are the currents.

    I recently put a bag of aluminized plastic in a microwave oven at home (it contained some frozen food) - pretty exciting to watch. :biggrin: But I don't recommend doing that, because one can damage the microwave oven or could cause a fire. Certainly there was enough energy to cause the plastic to burn slightly since the microwaves could not penetrate the metal - and the microwaves did heat the bag, but not the contents.
     
  7. Oct 13, 2005 #6

    Danger

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    So, Astro... was this an experiment, or were you just too hungry to waste time unwrapping it?:tongue:
     
  8. Oct 13, 2005 #7

    Astronuc

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    :rofl:

    Well both actually. :rofl: I was a bit impatient, but on the other hand, I was curious. I had to shut off the microwave quickly because of the electrical discharges - looked pretty cool though (like an aurora), but I could have easily toasted the electronics.

    If one has an old microwave, it would be an intesting experiment, but don't do this to a good piece of equipment.

    I can imagine my wife would have toasted me if I had destroyed our microwave oven. :biggrin:
     
  9. Dec 7, 2011 #8
    Can cold water circulating in close proximity of the polished metal be used to cool down the reflector surface and to avoid melting/overheating?
     
  10. Dec 7, 2011 #9
    *On the other side, not under the microwaves
     
  11. Dec 7, 2011 #10
    Any good conductor like metal surface is a good reflector of RF MW. The reason is because RF MW have a very very shallow penetration and mostly reflected back out.

    Long wave don't reflect as good with metal and the penetration depth is much deeper. I don't know slow frequency as much, I can just say things in 100MHz reflect well on metal.
     
  12. Dec 7, 2011 #11
    Not necessary, even though surface current formed by magnetic boundary condition, by if the surface resistance is low, not much power dissipated on the metal. It is just [itex] W=I^2R[/itex].
     
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