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Double-slit experiment question

  1. Jul 23, 2007 #1
    The question goes like this,
    From the 2-slit interference experiment, determine the position of the 1st maximum if lambda=400nm, d=1mm and D=10cm.

    I've been reading through the experiment through external sites and none had given an example near the question. The question is, should i use Young's formula? What should i do first?

    Thanks! ^_^
     
  2. jcsd
  3. Jul 23, 2007 #2

    mgb_phys

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    Draw a diagram - it's just trig.
    Put all the dimensions in the same units.
     
  4. Jul 25, 2007 #3
    how? i mean, draw a triangle and input the measurements? when the problem says find the maximum, is that the central maximum where n=0?
     
  5. Jul 25, 2007 #4

    Doc Al

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    Since the central maximum is always in the center, that wouldn't be much of a challenge, would it? The first maximum means the first non-central maximum: where m = 1 (or n = 1, depending on your notation) in the Young's double slit formula. (Read this: Double Slit Interference)
     
  6. Jul 25, 2007 #5
    ok. since there was a calculator there, i just inputted the values. back to the main question: the question asks the position. is the position in terms of what units? the angle and the y-displacement?
     
  7. Jul 25, 2007 #6

    Doc Al

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    I assume that they want distance from the central maximum, which is the y-displacement.
     
  8. Jul 25, 2007 #7
    ok thanks. last question. what is the physical explanation for the y-displacement? (sorry for this question. im just confused)
     
  9. Jul 25, 2007 #8

    mgb_phys

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    In simple terms it's the point on the screen where the difference in distance from each slit is 1 wavelength.
    Here the two rays of light are in phase - the high points of the waves coincide - they add to give a maximum (bright point).
    Where the difference is half a wavelength, the maxmum of one aligns with the minimum of another and they combine to give a minima (dark point)
     
  10. Jul 25, 2007 #9
    thanks for all the help!
     
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