image credits: Lawrence S. Anderson-Huang, The University of Toledo; image source
A spectrum shows light spread out according to its color. The continuous spectrum with dark absorption lines, which is shown twice above, is sunlight, and the emission lines, in the other spectra, are from the elements indicated--magnesium, hydrogen, and sodium. Can you find any of their emission lines in the solar spectrum?
For the difference between absorption lines and emission lines, see the diagram in Solar Spectrum.
Can you match any of these emission lines to absorption lines in the solar spectrum? For a simulation of the spectra of many common elements, see Spectra of Gas Discharges.
(This feature was updated on July 27, 2011.)
Spectral Lines, from Physics 2000, and the pages that follow it show how observations of spectral lines led to the concept of atomic energy levels. For more on energy levels, see Ohio State's Measuring Light: Spectroscopy. To find out how stars are classified by their spectral type, visit the Sloan Digital Sky Survey's Energy Levels of Electrons.