1. The problem statement, all variables and given/known data a) Exactly 4 bright fringes are seen on either side of the central maximum when a diffraction grating is illuminated with yellow-green light of a wavelength of 570 nm. What is the maximum number of lines/meter for the grating? 2. Relevant equations sin(theta) = m(wavelength) / d so solving for d = m(wavelength) / sin(theta) 3. The attempt at a solution I want to find the max number of lines/ meter for the grating so d= ? m/line m = 0 because the question says central maximum wavelength is given to you and in meters it is 570*10^-9 m ***what i dont understand is how do you find the angle Theta? Does it have to do with the "4 bright fringes" part of the question? And does that mean m=4? because after finding the angle Theta i would be able to solve for d = m(wavelength) / sin(theta) and get an answer. Then I would do 1/answer to get the final answer in lines/m.