An instructor is performing Young's double-slit experiment for his students. He directs a beam of laser light to a pair of parallel slits, which are separated by 0.102mmfrom 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 560nm.

 

(a)What is the optical path-length difference (inm) that corresponds to the third-order bright fringe on the screen? (This is the third fringe, not counting the central bright band, that one encounters moving from the center out to one side.) 

 

(b)What path-length difference (inm) corresponds to the third dark fringe that one encounters when moving out to one side of the central bright fringe?