Question

Explain the types of absorption spectrum.

Answer 1

When light is allowed to pass through a medium or an absorbing substance then the spectrum obtained is known as the absorption spectrum. It is the characteristic of absorbing substances. The absorption spectrum is classified into three types:

1. Continuous absorption spectrum:
   When the light is passed through a medium, it is dispersed by the prism, we get a continuous absorption spectrum. For instance, when we pass white light through a blue glass plate, it absorbs everything except blue. This is an example of a continuous absorption spectrum.
2. Line absorption spectrum:
   When light from the incandescent lamp is passed through cold gas (medium), the spectrum obtained through the dispersion due to prism is the line absorption spectrum. Similarly, if the light from the carbon arc is made to pass through sodium vapor, -a continuous spectrum of carbon arc with two dark lines in the yellow region of sodium vapour is obtained.
   
   
   
3. Band absorption spectrum:
   When the white light is passed through the iodine vapour, dark bands on the continuous bright background are obtained. This type of band is also obtained when white light is passed through a diluted solution of blood or chlorophyll or through certain solutions of organic and inorganic compounds.