1. Solar Spectrum
wavelength in Å
Joseph von Fraunhofer, 1814

2. Radiation from hot objects

3. Emission Spectra
Emission spectrum of Hydrogen

4. Emission Spectra Emission spectrum of Hydrogen
Emission spectrum of Iron

5. Kirchhoff’s Three Laws of Spectroscopy:
Light from a hot solid object has a continuous spectrum with no dark lines
The same light, passed through a cool gas has the same spectrum, but with certain wavelengths missing  dark lines (absorption spectrum)
Light emitted by a hot gas  bright lines superimposed on an otherwise black background  emission spectrum
UV
IR