Emission and absorption spectra AQA Alevel physics

What is emission and absorption spectra and how energy level diagrams relate to this. Note: This is particle physics for the AQA spec, advances in physics have happened, this is meant to be a revision tool. AQA A level specification - post 2015 Music: TheFatRat - Unity Spectra image: http://stokes.byu.edu/teaching_resour...