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Why are X-rays absorbed in the atmosphere.

  1. Aug 31, 2011 #1
    X-ray observations of outer space are usually made from orbiting platforms. Yet radio and optical astronomy seems to work pretty well.

    I got to thinking that it seems odd for the highest energy electromagnetic radiation to be so well blocked by earth's atmosphere...I would have thought: more energy the more radiation gets thru...but apparently not.

    Seems like the highest energy radiation (X-rays,gamma rays, and some UV) from space are blocked in the upper atmosphere protecting us from genetic damage; I would have thought it would take more dense atmosphere to block the most energetic radiation; again, apparently not:

    There is a nice diagram here:


    What's the mechanism(s) that accounts for this absorption?? Is it the upper atmosphere that also blocks high energy radiation emitted from earth??
  2. jcsd
  3. Aug 31, 2011 #2
    Photoelectric absorption, compton, pair production - the total extinction cross section for high-energy photons is large enough that the atmosphere is optically thick even though it's relatively low-density, because it's so deep. Lucky us. :smile:
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