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J.J. Thomson Experiment

  1. Apr 27, 2013 #1
    This experiment aims towards finding e/m ratio and it is a very well known experiment that's why I will directly post my question. Why do we evacuate the glass tube?
  2. jcsd
  3. Apr 27, 2013 #2
    electrons would be easily stopped in a tube containing gas.
  4. Apr 27, 2013 #3

    Doc Al

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    Staff: Mentor

    The better the vacuum, the better the electrons can travel unimpeded by collisions with gas molecules. A beam of electrons won't get far in air before being scattered.
  5. Apr 27, 2013 #4
    Uh, I see.. Great thanks.
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