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In a double slit experiment, a student measures the maximum and minimum intensities when two waves with equal amplitudes are used. The student then doubles the amplitudes of the two waves and performs the measurements again. Which of the following will remain unchanged?
  1. The intensity of the bright fringe
  2. The intensity of the dark fringe
  3. The difference in the intensities of consecutive bright
  4. and dark fringes
  5. None of the above
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Solution Video

OpenStax College Physics for AP® Courses Solution, Chapter 27, Problem 5 (Test Prep for AP® Courses) (0:55)

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Video Transcript
This is College Physics Answers with Shaun Dychko. A dark fringe means you have destructive interference. And so, when you have a wave with a higher amplitude used in the second iteration of this experiment, you expect the destructive interference to be just the same. So, intensity of the dark fringe is kind of a contradiction of terms because, well, it's like saying the amount of zero will be different. You can't have zero being any different than zero any other time. This darkness means zero amplitude of the super positioned waves at a certain point where there's the dark fringe. So anyway, the darkness of the dark fringe will not change. And so, the answer here is B.