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What allows certain wavelengths to pass through walls ?

  1. Nov 6, 2015 #1
    Radio waves can go through walls and x Rays go through body tissue but the visible spectrum is blocked by both . Why is this the case?
  2. jcsd
  3. Nov 6, 2015 #2
  4. Nov 6, 2015 #3


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    There are problems with his explanation, not the least being

    This is incorrect .... ALL electromagnetic radiation travels at the speed of light
    radio waves are NOT slow, gamma rays are NOT fast

    he repeats this error several times

  5. Nov 6, 2015 #4
    Good catch. I was in a hurry earlier, and admittedly, I didn't read the article.
  6. Nov 6, 2015 #5


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    no probs

    overall his explanation is pretty poor ... wonder if between us we can find something better for the OP ? :smile:

    I know of a good link that explains why glass is transparent to light ... the principles are
    going to be similar for other portions of the EM spectrum, I suspect ..... am not an expert
    in that area of physics :smile:

  7. Nov 6, 2015 #6
    I'll definitely get looking
  8. Nov 7, 2015 #7
    I'm guessing the author meant the frequency, not the propagation speed.

    I asked my professor something similar about photoionization cross sections ... i.e. increasing photon energy does not always mean an increased cross section. The reasoning he gave was along the lines of the wavelengths become too different for the photon and electron's orbit to interact.

    so it could be the case that the visible spectrum interacts with common electronic configurations and is thus blocked (high probability anyway) ... this also explains why it is visible (because it interacts!)
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