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Resolving Power - Disadvantages

  1. Apr 10, 2013 #1
    So I know resolving power is given by :

    Resolvance = λ/Δλ = nN

    Where n = order of fringe being observed and N is the no. of slits.

    So I was thinking there are a few ways of increasing resolvance :

    1.) Decrease the slit width
    2.) Increase the order of the fringe we observe.
    3.) Increase the number of slits.

    However, wouldn't the first option cause a decrease in transmitted light and hence wouldnt our spectra have decreasing intensity ?

    Also, for the second option, it is known that intensity of maximas decreases quite quickly from one order to the next... Hence, would our peak have poor intensity as well ?
     
  2. jcsd
  3. Apr 10, 2013 #2

    mfb

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    Right. You'll have to find the best slit width, taking both effects into account.
    Not if the slits are narrow ;).
     
  4. Apr 10, 2013 #3
    increasing the number of slits increases resolution AND intensity
     
  5. Apr 10, 2013 #4

    Andy Resnick

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    I'm not sure what you are asking about- technologies used for high resolution spectroscopy, grating design, something else....?
     
  6. Apr 11, 2013 #5
    I'm in interested in grating designs that could increase resolving power and the subsequent disadvtages.
     
  7. Apr 11, 2013 #6
    So what changes could I implement that would have some disadvantages ?
     
  8. Apr 11, 2013 #7

    mfb

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    Are you sure you want to get additional disadvantages?
    - reduce the number of slits
    - use a different width for different slits
    - make the slits too small, or too wide
    - use the screen too close to the grating, or too far away

    If you want to have advantages, avoid all those points.
     
  9. Apr 11, 2013 #8
    Thanks !! You see what I'm really interested in is the possible trade off's.
     
  10. Apr 11, 2013 #9

    Andy Resnick

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    Grating design is a complex subject that must take into account not just the density of 'lines' but also the detailed shape (the 'blaze angle', for example). I recommend starting by reading this:

    http://gratings.newport.com/library/handbook/handbook.asp

    It's the gold-standard reference. Also, I recommend looking at what equipment NIST or other standards labs use to perform precision (say, 1 part in 10^15) spectroscopy.
     
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