Hi, i exam is coming up in a week and i have no clue so wat ever on how to solve this question. How do i calculate the minimum number of lines??? What i need to answer to have full marks?? Q: The Sodium vapor spectrum contains two bright yellow lines which have almost the same wavelength (589.0 nm and 589.6 nm). Calculate the minimum number of lines required in a grating which can resolve these lines in the second order. :( if you have some spare time, please help me out.