Astronomy 123 Basics  

SPECTRAL ANALYSIS - CHEMICAL ID 

Each chemical element produces its own unique set of spectral lines. These spectral lines serve as a "fingerprint" - revealing the elements from which they are emitted. A spectrograph is an optical device that records a spectrum. 

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Old fashioned spectrograph

• Light dispersed by prism 
• Deficiencies:
  • uneven spread of frequencies
  • uneven absorption of frequencies

Modern Device

• based on diffraction grating
• thousands of closely spaced lines cut into glass

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The emission spectra of some well known elements.

The visible spectrum of the Sun.

The emission and absorption lines of Sodium.

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From the observed spectrum (analyzed with a spectrograph) we can determine the chemical elements involved.

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