1. The problem statement, all variables and given/known data White light was shone vertically down on a cd tilted 5°, with adjacent tracks d = 720 nm. An observer some distance away observes a color of light. Determine that wavelength of light observed. (Refer to picture attachment) 2. Relevant equations finding path difference 3. The attempt at a solution I understand that finding the path difference is key to solving this problem. So, i found the path difference to be simply: d cos (90+ 5 - ∅) = (1)(λ) But the answer wrote path difference = d cos (90 + 5 - ∅) - d cos (90 - 5) Using the provided answer, it didnt make sense to me for the additional term of ' d cos (90 - 5)' to be there?