1. The problem statement, all variables and given/known data Iron produces many lines in the visible spectrum when given energy. Suggest why a sample of iron sulphate only produces lines in the green section of the spectrum. Sorry if it doesnt sound very scientific, im recalling the question from memory since ive already handed up the assignment. Assume that the answer has nothing to do with the sulfate or water present. 2. Relevant equations 3. The attempt at a solution Im doing yr12 physics in South Australia, so far in 'the structure of the atom' we have learnt about the absorption and emission spectrum. This is one question from our homework assignment, and i refused to answer it because i believe the answer involves a great deal more than just what we've learnt so far. iron in iron sulphate has 2 less electrons, and i dont believe that its as simple as saying that its 'combinations' or 'possibilities' of different energies of photons released has changed because of the different ratio of protons/electrons attracting each other. I think this is a question that the teacher made up, no its not a very good one, and i reckon a question like this will definetly not be in the exam.