Explain emission line spectra and absorption spectra.

Explanation

Each element emits radiation with different wavelength 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 certain specific wavelengths only.
A spectrum of this kind is known as emission line spectrum.
The spectrum emitted by atomic hydrogen is shown in figure.
Emission line spectrum of any gas is studied to identify that gas.
When white light passes through a gas we find in transmitted light certain wavelengths which is characteristic of the atom are absent. So there are some black lines appearing in the spectrum of scattered light.
The spectrum produced by these dark lines is called the absorption spectrum of the material of the gas.