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Find angular seperation of spectral lines with a grating spectrometer

  1. Apr 21, 2009 #1
    1. The problem statement, all variables and given/known data

    find the angular separation between the red hydrogen-alpha spectral line at 656nm and the yellow sodium line at 589nm if the two are observed in third order with a 3500-line/cm grating spectrometer.


    2. Relevant equations
    maximum equation for multi-slit interference
    d sin(theta)=m*lamda

    d=distance between two slits
    m=the interger called the order (bright spots)
    theta=angular seperation
    lamda=wavelength

    3. The attempt at a solution

    I tried plugging all of my data into the equation above with d as 1/grading but I'm not sure if this is the right way to go about the problem. I'm not even sure if this is the best formula to use but I cant find any other relevant equations
     
  2. jcsd
  3. Apr 24, 2009 #2

    djeitnstine

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    Gold Member

    Welcome to Pf sailfast

    you are correct, your d is 1/3500 to get centimeters per grating. This equation is correct and applies to this problem. Just be careful with your units and 'm'
     
  4. Apr 24, 2009 #3
    yay! i rock at PHYS
     
  5. Aug 6, 2009 #4
    I have the same question here. But when I get sin(theta), I get something over 1. That is not possible. Is my equation wrong? Because I am very sure the units I've been using here are correct. I converted everything into meters.
     
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