1. The problem statement, all variables and given/known data Two narrow slits are 0.4 mm apart. The dark fringe of order 5 is 1.2 degrees from the central bright fringe. What is the wavelength of the light in nm? 2. Relevant equations dsin(theta) = (m +1/2)lambda where d = distance between silts m=order lambda = wavelength 3. The attempt at a solution It seems simple enough right? I converted the 0.4mm into meters and plugged all the values into the equation which gives me: (4x10^-4)(sin1.2) = (5 + 1/2)lambda then lambda = (4x10^-4)(sin1.2)/5.5 Since the answer i get is in meters i have to multiply it by 10^9 right? but that answer is way too big. What am I doing wrong?