Two slits are separated by 0.180 mm. An interference pattern is formed on a screen 80.0 cm away by 656.3-nm light. Caclulate the fraction of the maximum intensity 0.600 cm above the central maximum. So to my understanding we know the wave-length = 656.3nm We know the distance between the two slits = .180 mm and we know how far away we are from the screen .800 m I know Light intensity(maximum)= I=I_max*(cos^2(pi*d*sin(thetha)/lambda)) I know the relatship between phi and lambda as well.. but I don't know how to go from here. Maybe I am heading the wrong directon with is? Any suggestions would be helpful. Thank you.