J.J thomsons Catode ray - Why hydrogen gas?

  1. Hi,

    I'm curious about J.J thomsons Catode ray, and i have a few questions:

    In J.J. Thomsons Catode ray setup he has hydrogen gas in a chamber through which the catode ray is beamed. What is the role of hydrogen gas? What could he use the hydrogen gas for?

    And how could he make up the assumption that The distance the electron is deflected when charging the metal plates in the catode ray tube, is proportional to the charge of the electron and inversly proportional to the mass of the particle?

    I'm watching the MIT lecture, and I was just very curious about this :)
    Last edited: Jul 16, 2014
  2. jcsd
  3. UltrafastPED

    UltrafastPED 1,912
    Science Advisor
    Gold Member

  4. Cathode rays were first discovered when trying to conduct electricity through rarified gases.
    An occasional positive ion will be attracted to the cathode, and this can knock loose electrons, the electrons can knock loose electrons from the gas, producing positive ions, wich get attracted to the cathode again. This happens also in neon and fluorescent lamps.
    look up "cold cathode" or "gas discharge lamp"

    This method also produces positive hydrogen ions, wich thomson was able to detect as well.

    The more efficient method of producing cathode rays with a heated cathode in a vacuum wasn't in use yet.

    This is a consequence of threating the electron as a point mass in a constant electric field, and using F = ma.

  5. Thank you so much for that great explanation.

    That sounds really interesting. So does it mean that he rearranged newtons equation for force to a=F/m and assumed that force must be the charge of the electron? Is there a derivation for it or is this how simple it was?
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