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Homework Help: Deflection of an electron due to gravity.

  1. Jan 16, 2008 #1
    1. The problem statement, all variables and given/known data
    There are two parts to the question.
    A)Why is gravity not important during JJ Thomsons experiment?
    b)what is the deflection due to gravity?
    Given variables.
    In a thomson spectromoter set at 10^4 (V/m). deflection with out the magnetic field applied equals .10 radians over a L of .050 m.
    Speed of electron with magnetic field applied is 2.9x10^7 m/s.
    Strength of Magnetic field is 3.4x10^-4 T.

    2. Relevant equations
    I don't know what they are....

    3. The attempt at a solution
    A) in the experiment the effects of gravity were negated by the application of a magnetic field perpendicular to that of the electric field, to help over come any deflection caused by gravity.
    B) I really don't know how to go about this.
    I thought about it a little more...would I just be using the velocity, time distance and deflection angle to solve this??
    Like...a particle fired at a zero degree angle?
    Last edited: Jan 16, 2008
  2. jcsd
  3. Jan 17, 2008 #2
    Alright so as far as I have it figured.
    v(y) = gt

    then take v(y)/v(x) and take the inverse tan of it to get the answer.
    It gives the angle of deflection in radians. The answer I got does not match that of the book but is close enough. It's a very small number.
    the answer the book was looking for was 10^-15 m.

    Now if it's done by taking .5(at^2) i get another answer, but the order is wrong. It comes out to something like 1.7x10^-17 or something or other.

    Any ideas what exactly they did??
  4. Jan 17, 2008 #3
    is it a GR problem or wat do you need to use GR Action or What???
  5. Jan 18, 2008 #4
    General Relatvity??
    No it is not. The speed is to slow.
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