Trigonometry

Red light I(lambda = 664 nm in vacuum) is used in Young's experiment with the slits separated by a distance from the screen given by D = 2.75 m. Find the distance y on the screen between the central bright fringe and the third-order bright fringe. Reasoning: This problem can be solved by the first using Eq. (i) to determine the value of theta that locates the third-order bright fringe. Then, trigonometry can be used to obatin the distance y.