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Interference and diffraction of light

  1. Jan 20, 2009 #1
    1. The problem statement, all variables and given/known data
    green light of wavelength 5000 A is incident normally on a grating, and the 2nd order image is diffracted 32 degrees from the normal. how many lines/cm are marked on the grating

    A=10^-10 n= 2 degree= 32 d=? wavelength- 5000 A

    the answer to the question is 5300 lines/cm

    2. Relevant equations

    wavelength=d sin degree/ n

    3. The attempt at a solution

    we tried to solve for d using the following above equation but came out with the wrong answer, need help please i am in a fatal situation here,
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jan 20, 2009 #2

    Doc Al

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    Staff: Mentor

    d is the distance between slits, not the number of slits per cm.
     
  4. Jan 20, 2009 #3
    So then what would I do to get an answer with lines/cm
     
  5. Jan 20, 2009 #4

    Doc Al

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    Given the spacing between lines, figure out how many fit into a centimeter.
     
  6. Jan 20, 2009 #5
    the spacing between lines is X?
     
  7. Jan 20, 2009 #6
    I don't understand then what equation i am to use to solve for such
     
  8. Jan 20, 2009 #7

    Doc Al

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    Here's an example: If d = 1/100 of a cm, how many lines are there per centimeter?
     
  9. Jan 20, 2009 #8
    100? but you said that d is the distance between slits, not the number of slits per cm. so what am i trying to find for this situation?
     
  10. Jan 20, 2009 #9

    Doc Al

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    Right. If you can do this example, use similar reasoning to solve your problem.
    That's true. You use d to calculate the number of slits per cm.
    Your final answer will be the number of lines per cm. You start by finding d.
     
  11. Jan 22, 2009 #10
    sorry im still confused on how to get there, what would i possibly do with d?
     
  12. Jan 22, 2009 #11

    Doc Al

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    Try this analogy: Along a path there is a tree every 1/4 mile. How many trees per mile?

    Here "1/4 mile" plays the same role as "d".
     
  13. Jan 22, 2009 #12
    there would be four, but so i solved for d and i get 1.81x10^-6, so now i convert that into cm?
     
  14. Jan 23, 2009 #13

    Doc Al

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    Staff: Mentor

    Careful how you round off.
    Yes, find d in cm.
     
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