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Homework Help: A laser emitting light with a wavelength of 560 nm (Single slit).

  1. Feb 13, 2017 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    a) see attached.


    i) Decreasing the width of the slit will cause less interference fringes to be seen, increases the distance amongst fringes and the fringes become wider.

    ii) If the screen was moved further away, fewer fringes will be visible on the screen, increased the distance amongst bright fringes, and the fringes that are developing the interference pattern become wider.

    iii) Increasing the wave length will cause the fringes that make up the interference pattern become wider, less fringes visible on the screen and an increased distance amongst bright fringes.


    A double slit with a light shone through it will result in having the interference pattern being evenly spread out and have like intensities.

    ii) Light shone through diffraction grating will result in evenly brighter fringes that are widely spaced and narrower.

    I was wondering if there's anything that i missed? I feel I have it all but I just want to be sure. Also, for questions B and C, i had a hard time learning the concepts during class as the videos my teacher showed hurt my eyess so it was kind of hard to see the differences in the waves/ dark and bright fringes. FRINGES.jpg

    Attached Files:

  2. jcsd
  3. Feb 13, 2017 #2


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    Staff: Mentor

    If the central maximum is 5 cm wide, how can the distance between adjacent maxima be 2.5 cm? That is less than the width of the maximum.
    Why? It is not necessarily wrong, but it is also not generally true.
    Perfectly? Or is it more complicated?
  4. Feb 13, 2017 #3
    Hmm did I approach it wrong? From what i have in my notes, the central maxima is twice as wide as the other maxima. Since Central Maxima was given I used the formula 2(Triangle)y to find the distance between the other maxima. :/ unless I'm forgetting something crucial.

    I upon looking at this question again and more examples, (If the screen was moved further away.) the intensity of the fringes is not as pronounced and thereby making it seem to have less visible fringes. Hmm is this more accurate? Or am I not seeing something?

    It's more complicated. I mean, the interference pattern created when light is shined through a double slit, is actually an overlap, and therefore the interference, of two single slit interference patterns. The two patterns is what diminishes the central maxima from each of the single slit patterns to make an evenly distributed double slit pattern. Hmmm i should of included this into my answer... What do you think?
  5. Feb 13, 2017 #4


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    Staff: Mentor

    Ah, so your "distance between maxima" applies to all other maxima? Then it should be fine.
    The intensity goes down, making the fringes harder to see, yes. But the number of existing fringes stays the same, some just get too dim to be visible.
    That description confuses me. The point is that the two slits have a finite width. You still get effects from their single-slit behavior.
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