Absorption and Emission Lines Absorption and Emission Spectra
Courses and more...
Yet More...

Absorption and Emission Spectra

Absorption lines were discovered first by an English chemist called William Wollaston in 1801 but he failed to recognise the significance of them, and it was their rediscovery by Joseph von Fraunhoffer in 1814, and they still carry his name today, being known as Fraunhoffer lines

hydrogen absortion spectrum showing the Fraunhoffer lines

Emission lines were discovered as chemists (initially John Herschel and William Fox Talbot) starting to examine the patterns of coloured lines given off as chemicals were burned, and gradually the emission spectra for the elements emerged.

hydrogen emission spectra showing the correspndence of emission and absorption lines

The connection between the emission lines and asorption lines was provided by Robert Bunsen and Gustav Kirchoff and Kirchoff worked very hard to ensure that other people would be able to understand and use spectral analysis. In so doing he clarified 3 important truths that tie together the absorption and emission spectra:
  1. A hot solid object or hot dense gas produces a continuous spectrum - a rainbow
  2. A hot tenuous gas produces a series of brightly coloured lines (depending on it's chemical composition) - an emission spectrum
  3. A hot solid body surrounded by a cooler tenuous gas gives an absorption spectrum

You can find out far more about these discoveries and how they relate to our understanding of the sun, as part of the big story about the development of our ideas about our nearest star in the brilliantly written and easy to read book by Dr Stuart Clark