1. The problem statement, all variables and given/known data Light from a helium-neon laser (λ=590 nm) is used to illuminate two narrow slits. The interference pattern is observed on a screen 3.42 m behind the slits. Twelve bright fringes are seen, spanning a distance of 47 mm. What is the spacing (in mm) between the slits? 2. Relevant equations 3. The attempt at a solution t = wavelength t= 590 nm L = 3.42 m y = 47 mm 12 fringes so the space between 2 fringes would be 47mm/11 = 4.27 mm d = tL/y = 4.73 x 10^-4 m I don't have the answer to this problem so is this the right way to do this???