Explain emission line spectra and absorption spectra.

(N/A) Each element emits radiation with different wavelengths depending on its temperature. Hence,each element has a characteristic spectrum of radiation which it emits.
When an atomic gas or vapour is excited at low pressure by passing an electric current through it,the emitted radiation has a spectrum which contains only certain specific wavelengths. $A$ spectrum of this kind is known as an emission line spectrum.
The emission line spectrum of atomic hydrogen is shown in the figure.
Emission line spectra of any gas are studied to identify that gas.
When white light passes through a gas,we find that certain wavelengths,which are characteristic of the atom,are absent in the transmitted light. Thus,there are some black lines appearing in the spectrum of the transmitted light. The spectrum produced by these dark lines is called the absorption spectrum of the material of the gas.