Problem 2: Monochromatic light of wavelength 589.2 nm is used to illuminate the narrow slits 1 mm apart. Find the position of the first dark and first bright fringes on a screen 100 cm away.
Wavelength of the incident light = 589.2 nm
Slits separation = 1 mm = 10-3 m
Distance between slits and screen = L = 100 cm = 1 m
Position of the first dark fringe = Ydark 1 =?
Position of the first bright fringe = Ybright 1 =?
For dark fringe,
For bright fringe,
Now to find the first dark fringe, put m = 0 in formula (1).
Similarly, to find first bright fringe, put m = 1 in formula (2).