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Properties of Cathode Rays

  1. May 24, 2012 #1
    Why are cathode rays able to penetrate very thin metal films?
  2. jcsd
  3. May 24, 2012 #2
    because thin metal films are mostly empty space
  4. May 24, 2012 #3
    Is this the empty space within the atom (ie the space between the nucleus and the electrons) or the space between the atoms in the metal lattice?

  5. May 24, 2012 #4
    It seems as if you have a picture in your mind of the lattice as being the same as the common figure given as atoms being points connected by lines, with a whole lot of empty space. . Or is it the other common picture as atoms being hard balls to show the packing structure with empty space between the spheres.
    Both are just geometrical representations.

    A whole bunch of nucleii in specific locations surrounded by electron clouds in the 'space' between is short and sweet, and hopefully answers your question and does not cause the ire of most physicists as lacking detail, which is evident.
  6. May 25, 2012 #5
    Thanks for the reply

    I was thinking of the structure where the atoms are represented as hard balls, in order to show the packing structure of the unit cell of the lattice. Based on the type of unit cell (eg face centred cubic or body centred cubic), it is possible to calculate the percentage of empty space in the unit cell of a lattice. However, such a representation is an oversimplficiation as it does not take into account the difficulty in defining the volume occupied by the electron cloud.

    If electron clouds are considered, is there actually any spaces between the atoms (or more correctly ions) in the metallic lattice? If there is no space between atoms, then the cathode rays are really passing through the empty space within the atom, rather than spaces between the atoms. This is what I am trying to clarify.

  7. May 25, 2012 #6


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    Staff: Mentor

    That depends on what you mean by "empty space". The space inside an atom is full of possible positions for electrons and nuclei in addition to the different forces between each particle. You could also consider the space between each atom the same way.
  8. May 25, 2012 #7
    So Drakkith, are you saying that the space between atoms is actually the space between the nucleus and the electrons in an atom because the volume of space in which an electron could be is cannot be exactly be defined (we only know regions where electrons are most likely to be found).

  9. May 25, 2012 #8


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    Staff: Mentor

    I'm just saying that trying to determine whether an electron passes through "empty space" when it passes through a thin metal sheet depends entirely upon what you define as "empty space". At the quantum level things are not always defined the same way as they are at our own scale. Empty space within and between atoms is full of potentials and fields and whatnot. I wish I knew quantum physics a little better, perhaps I could explain it more accurately.
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