[SOLVED] Diffraction Grating 1. The problem statement, all variables and given/known data Find the number of slits per centimeter of a grating designed to disperse the first-order visible spectrum through an angular range of 15.0. Find also the angles at which the first-order visible spectrum begins and ends. 2. Relevant equations d sin [tex]\theta[/tex] = n [tex]\lambda[/tex] d = 1/N 3. The attempt at a solution Okay, if it's first order, then n = 1, I suppose, but lambda and theta are unknown and I need to get d to find N... For the second part, once I have d, I can input 400 and 700 nm for lambda to get the two values for theta, but obviously I need d for both answers and I have no clue how to get it. Any help would be appreciated. Thanks!