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Wavelength and frequency

  1. Feb 19, 2008 #1
    1. The problem statement, all variables and given/known data

    Find the frequency and wavelength of a 100 MeV gamma ray photon

    2. Relevant equations


    100 MeV=1.602 X 10^-11
    3. The attempt at a solution

    I do not know how to do this. I am in a class for elementary teachers and we have to solve this problem.
     
  2. jcsd
  3. Feb 19, 2008 #2
    Do you have any equations that relate wavelength to frequency?
     
  4. Feb 19, 2008 #3
    I do not know any.
     
  5. Feb 19, 2008 #4
    Well you should certainly have an equation for relating wavelength and frequency, the less obvious thing is relating the energy of a photon to the frequency/wavelength

    You should also have an equation for that, it involves planck's constant, h
     
  6. Feb 19, 2008 #5
    Wave length equals frequency times 340 meters per second...
     
  7. Feb 19, 2008 #6
    Unfortunately that's the specific equation for sound waves, pretty much at sea level. The topic creator is dealing with electromagnetic waves
     
  8. Feb 19, 2008 #7

    mgb_phys

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    The equation for frequency and wavelength is simply speed = wavelength * frequency
    A gamma ray photon is a kind of light so you need the speed of light.

    There is also an equation relating it energy, energy = h * frequency
    where 'h' is a constant = 6.6 x 10 ^-34 Js

    Remember that all you values must be in the same units ( metres, seconds, Joules) for these constant to work
     
  9. Oct 6, 2009 #8
    We're doing this in my A-level at school.

    First find the frequency using, Energy (J)=Planck Constant (Js) X Frequency (Hz)
    Or, E=hf.
    The planck Constant is (6.6 x 10^-34).
    ---------------------------------------------------
    So:
    (1.602 X 10^-11)J = (6.6 x 10^-34)Js X f

    Or

    (1.602 X 10^-11)J / (6.6 x 10^-34)Js = f

    So the frequency is (2.47 X 10^22)Hz.
    ----------------------------------------------------
    Speed (ms) = Frequency (Hz) X Wavelength (m)

    So:

    Speed of light-> (3.0 X 10^8)ms / (2.47 X 10^22)Hz = Wavelength (m)

    =(1.215 X 10^-14)
     
  10. Oct 6, 2009 #9

    Redbelly98

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    Welcome to PF, Dumbfish1.

    FYI, we don't simply post solutions here when people ask for homework help. We give hints, and require that the asker make some attempt toward solving the problem first.

    Since this question is from more than a year ago, I guess there was no harm done. You might want to familiarize yourself with the forum rules; simply scroll down to the section "Homework Help" here:

    https://www.physicsforums.com/showthread.php?t=5374
     
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