1. The problem statement, all variables and given/known data A laser is shone through a set of slits and onto a screen. I have a Δy vs. L graph plotted, where Δy is the spacing between successive nodes, and L is the distance from the slits to the screen. I'm supposed to find the spacing between the center of the slits. The value of λ is given. 2. Relevant equations Δy = λL/D y is the spacing between successive nodes L is the distance from the slits to the screen D is the spacing between the center of the slits 3. The attempt at a solution I have the slope, but I don't know where to go from there... I'm thinking that the slope will be equal to λ/D? and if I know λ, then I can calculate D. Not sure if this is the right way to go though.