The Spectra can usually be divided into line and band Spectra. On the one hand, line Spectra are said to possess sharp and well defined lines, band Spectrum on the other hand consists of closely spaced lines referred to as bands. Line Spectrum is the characteristic of the Atoms, while the band Spectrums are the characteristic of the Molecules. The formation of the line Spectra is due to the excitation and de-excitation of the Electrons present in the Atoms. Band Spectrums are formed as a result of the vibrations and rotations of the Molecules. Line Spectra are also often known as the Atomic Spectra. The band Spectra on the other hand is also known by the name of molecular Spectra.