In a double-slit experiment it is found that blue light of wavelength 478 nm gives a second-order maximum at a certain location on the screen. What wavelength of visible light would have a minimum at the same location? ----- I have no clue how to approach this problem but looking in the book I assumed the wavelength with a minimum at that same location should be 3rd order (m=3) so I set up an equation as follows: m1*Lambda(max) = m2*Lambda(min) Lambda(min) = m1*Lambda(max)/m2 = (2*478*10^-9)/3 = 319 nm Apparently it's wrong. I'm lost on where to go from here.. Any help ??