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Homework Help: Visual Displays - help meee!

  1. Mar 14, 2005 #1


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    I'm doing an A-level coursework (Uk sort of 17/18-year old level thing) on visual displays, and I'm confused.

    Can anyone clarify the physics of the phosphor on the screen of a CRT, to which energy level the electron is absorbed and why, why the electron decays, why the electron is emitted again and with how much energy, how to relate this to the energy it has before it's absorbed, etc.
    And how are the deflecting coils arranged? What is their orientation and do they coil around the tube or around in a circle next to the tube or something else? Is the cathode heated or is the PD between cathode and anode enough to get the electrons to move?

    Also, can you explain the exact nature of the liquid crystals in LCDs, because this is very confusing to me? I seem to have arrived at the conclusion that there are such a thing as Smectic C Chiral Nematic liquid crystals between the glass plates, but Smectic and Nematic seem to be contradictory. What do these terms mean, which ones am I dealing with, what is the "director" which lines the molecules, how does it work, do the molecules start facing with their longest bit parallel to the glass and then when they line up, have their longest bit perpendicular to the glass, and is this what Smectic C means (I know that they twist when influenced by the "director", but only in the plane that is parrallel to the glass, and I'm talking about whether they move in a plane which is perpendicular to the glass - is this "director" an electric field or an electric current or something else?)?

    Sorry if this is confusing, but it reflects my state of mind right now :yuck:

    Thanks very much in advance for any help you may give me.

    If this should go in any other forum, I'm sorry, and I don't mind if it's moved.

    EDIT: oh, and I'm also going to go on to talk about projection TV, holograms, and then briefly go over any other interesting futuristic display ideas I can find. So if anybody can help with that, it would be much appreciated :D.
    Last edited: Mar 14, 2005
  2. jcsd
  3. Mar 19, 2005 #2

    Andrew Mason

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    I am not sure I understand what you are asking. An electron is accelerated by the potential difference between the cathode and anode. It is focused and directed by magnets and the electrons crash into a phosphor coated screen, exciting the phosphor atoms and causing them to give off radiation, mainly light.

    The cathode is heated. There are many good sources that will explain how a cathode ray tube works. see, for example:

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