1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What was the angle of deflection?

  1. May 24, 2014 #1
    The problem statement, all variables and given/known data
    The scientist changes the frequency of the incident X-ray to 4.50 x 10^19 Hz and measures the deflected X ray frequency of 4.32 x 10^19 Hz. What was the angle of deflection?

    Fi = 4.50 x 10^19 Hz
    Ff = 4.32 x 10^19 Hz

    2. Relevant equations
    Δλ = λf - λi
    Δλ = (h/mc)(1-cosθ)
    λ = c/f

    3. The attempt at a solution

    First, I found the wavelength of the X ray before and after it is deflected.

    λi = c/f
    = (3.00 x 10^8 m/s) / (4.50 x 10^19 Hz)
    = 6.818181812 x 10^-12 m

    λf = c/f
    = (3.00 x 10^8 m/s) / (4.32 x 10^19 Hz)
    = 6.9444444444 x 10^-12 m

    Then found the change in wavelength

    Δλ = λf - λi
    = (6.944444444 x 10^-12 m) - (6.818181812 x 10^-12 m)
    = 1.26262626 x 10^-13 m

    Then I used the change in wavelength to find the angle

    Δλ = (h/mc)(1-cosθ)
    1.26262626 x 10^-13 m = ((6.63 x 10^-34 Js) / (9.11 x 10^-31 kg)(3.00 x 10^8 m/s))(1-cosθ)
    1.26262626 x 10^-13 m = (2.4259056 x 10^-12)(1-cosθ)
    0.052047623 = 1-cosθ
    cosθ = 0.947952377
    cos^-1(0.947952377) = 18.56692499° = 18.6°

    I'm just really unsure of the process that I took...
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. May 24, 2014 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Welcome to PF;
    Please do not leave out vital information - I am guessing that this is a Compton effect problem.

    The way to be more sure of the processes you used, is to write down your reasoning for each step: why did you choose that particular equation?
    You should also consider if the answer makes sense in terms of the physics - i.e. if you already know the deflection angle for another frequency, you can compare the deflection angles ... how does the deflection angle generally depend on the frequency: i.e. does a higher frequency produce a bigger or a smaller angle?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: What was the angle of deflection?
  1. Deflection Angle (Replies: 3)

  2. Angle of deflection (Replies: 3)

Loading...