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Homework Help: Light wave interference

  1. May 10, 2006 #1
    Hello, I need help with a light wave interference question.

    Q: Imagine you are trying to measure the width of a single strand of spider web. You have fastened the web to the slide horizontally. You illuminate the strand with a 650nm laser and project the resulting interference pattern onto the wall where you have fastened a piece of paper. Given that the strand is
    65 μm wide and is located 2 meters from the wall, draw the resulting interference pattern you would see in. Draw the pattern to scale in the correct orientation. Include only the m=-2, -1, 0, 1, 2 maxima (bright spots). Indicate the distance between each adjacent maximum.

    Usually I would say what I know and how I would approach this problem, but for this one I really am at a lost. Any help is greatly appreciated
  2. jcsd
  3. May 10, 2006 #2


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    The spider web thread is opaque; it will cast a shadow.
    Outside the edges of the thread are paths that diffract into the shadow.
    They each have a path length from thread to screen (like single-slit)
    the path Length difference (L_top - L_bottom) causes interference.
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