Lines Spectrum

 
You know that when we pass a beam of sunlight through a prism we get a range of colours from violets to red (VIBGYOR) in this form of a spectrum (like rainbow). This is called a continuous spectrum because the wavelengths of the light varies continuously that is without any break. Let us take another example. You are aware of the flame tests for identifying cations in the qualitative analysis. Compounds of sodium impart a bright yellow colour to the flame; copper gives a green flame while strontium gives a crimson red coloured flame. If we pass such a light through a prism it gets separated into a set of lines. This is called as a line spectrum. Different between a continuous and a line spectrum.

Lines Spectrum of Hydrogen Atom: when an electric discharge is passed through a discharge tube containing hydrogen gas at low pressure, it emits some light. When this light is passed through a prism it splits up into a set of five lines. This spectrum is called the line spectrum of hydrogen