wavelength of light, and o is the distance between the slits S, and S. If 8 is small, then sine = tane. Thus, the formulas for constructive interference and destructive interference becomes: Constructive Interference for Young's Experiment (for bright finges): Destructive Interference for Young's Experiment (for dark fringes): where: y.. is the distance of the fringe being considered from the central bright fringe and R is the distance of the slit to the screen. note: The value of m specifies the order of the fringe (zero for the central bright fringe, 1 for the first side maximum, 2 for the second, and so on). The central bright fringe has the greatest intensity of light. Intensity decreases symmetrically on either side of the central bright fringe. Ex 1: A double-slit experiment is performed using light wavelength 664 nm. The distance between the slits is 1.2 mm, and the screen is located 2.5 m from the slits. Find the (a) angle that locates the third order bright fringe on the screen, (b) distance between the central bright fringe and the third order bright fringe, and (c) distance between the second and third order bright fringe. Ex 2: A double-slit experiment is performed using a light wavelength 664 nm. The distance between the slits is 1.2 mm and the screen is located 2.50 m from the slit. Find the (a) angle that locates the third order dark fringe on the screen, (b) distance between the central bright fringe and the third order dark fringe, and (C) distance between the third order bright fringe and third order dark fringe