Light emitted and absorbed is atom/molecule specific.

1
Light emitted and absorbedis atom/molecule
specific.
Furthermore, Relative intensities tell us about
relative abundances of the elements.
2
Energy is conserved!
Continuous all possible colours. Absorption
certain colours are absent (black
lines). Emission discreet colours on a black
background.
3
Discrete Spectra
Characteristic Yellow lines of Sodium
4
Characteristic Lines of Atoms
5
Molecular Line Spectra have Richer Structure.

• Due to additional rotations and vibrations of the
  nuclei.
• Signature for cooler regions in space.

Molecular and Atomic Hydrogens emission spectrum.
6
Solar Spectrum!