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Gamma/Radio waves through solids

  1. Jul 20, 2010 #1
    Why is it that gamma and radio waves can pass through some solids so easily compared to visible light? I understand that the wavelengths are different than visible light, but why does that effect things?

    Do they simply not interact with anything in the material? Or, if they do, what to they interact with?

    Also, do they change speed when traveling through the material. I guess that question depends on the second.
  2. jcsd
  3. Jul 20, 2010 #2
    This paper talks about shooting all kinds of photons through matter .
    http://pdg.lbl.gov/2009/reviews/rpp2...les-matter.pdf [Broken]
    Bob S showed me this ,
    And also you can shoot high-energy gamma rays at some material and when they scatter off protons they can produce electrons and positrons .
    Last edited by a moderator: May 4, 2017
  4. Jul 21, 2010 #3
  5. Jul 21, 2010 #4
    EM waves interact with matter primarily through interaction with electrons.

    In some materials, (some of the ) electrons are fairly free to move - conductors for example. In those, the energy of the radiation is absorbed exponentially with depth according to the wavelength. Longer wavelengths which only move the electrons slowly are able to pass through fairly easily - radio waves can go through thin sheet metal, light can't.

    In other materials, the electrons are bound to atoms but can still move to some extent although the ways they can vibrate are restricted - that leads to selective absorption and reflection depending on frequency - different colours, different transparencies etc.
    This will depend in a very complex way on the exact nature of the molecules involved.
    In some simple cases we can make predictions (Compton scattering for example), in many we can only make measurements and produce tables of behaviours.
  6. Jul 21, 2010 #5
    Then how come when i wrap my cell phone in aluminum foil it cant get the call .
  7. Jul 21, 2010 #6
    Modern comms devices use ultra-high frequency radio waves. An old-fashioned valve radio picking up the light program on 200kHz wouldn't even notice.
  8. Jul 21, 2010 #7
    Can the transmission process (through a material) be thought of as analogous to sound waves propagating through a medium, where one particle gives the energy to the next? Only with electrons as opposed to whole molecules.

    Then, absorbtion analogous to the disorganized transfer of energy in a lattice?

    Then, reflection, similar to resonant surface reflection?

    Sorry, my brain always tries to take these things and run with them, which is sometimes wrong.
  9. Jul 21, 2010 #8
    More or less - a reasonable analogy.
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