Spectroscopy is the study of Interaction between electromagnetic radiation and matter. Thus, matter can be anything like atoms, molecule or ions. It is not possible to see the spectrum phenomena of atoms in normal eyes. So, Spectrometer ( device ) is used to plot a graph in between amount of light absorbed and wavelength. Every atomic particles have unique absorbing pattern with respect to wavelength. The graph plotted in spectrometer thus help for identification of type of atoms, molecule inside the sample.