How can a spectrograph experiment identify a particular metal ion?

  thats weird im doin the same lab right now well idk this is wat i wrote 
The way electron light is emitted from metal salts is when an element is heated, the electrons will be excited. Then as these electrons fall back from one energy level to another, they will emit photons of light. Those photons will have different colors depending on the elements and its discrete energy levels. The way a spectrographic experiment can help identify a particular metal ion is because this device separates light into different wavelengths and gives you their measurements. With this it is easier to classify to line emission spectra.