Principle purpose of this lecture is to focus on Spectral Lines. A spectrum is the amount of light given off by an object at a range of wavelengths. A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. A Continuum Spectrum: Light emitted across a continuous range of wavelengths. A thermal spectrum is a continuum spectrum. Finally describe on Spectral Line formation.