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An instructor is performing Young's double-slit experiment for her students. She directs a beam of laser light to a pair of parallel slits, which are separated by 0.148 mm from each other. The portion of this light that passes through the slits goes on to form an interference pattern upon a screen, which is 4.50 meters distant. The light is characterized by a wavelength of 585 nm. (a) What is the optical path-length difference (in um) that corresponds to the fifth-order bright fringe on the screen? (This is the fifth fringe, not counting the central bright band, that one encounters moving from the center out to one side.) um (b) What path-length difference (in um) corresponds to the fifth dark fringe that one encounters when moving out to one side of the central bright fringe? um