Spectrographs

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Spectrographs
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Diffraction Gratings What are they?

• A thin piece of film
• Etched grooves
• Holographic etching
• Light bends into its component colors
• ACTS LIKE A PRISM
• The spacing between the grooves must be smaller
  than the wavelength of incoming light.

www.wikihttp//en.wikipedia.org/wiki/Diffraction_g
rating
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How else can a diffraction grating be made?

• You could etch grooves into any material
• Consider that we will be using gratings w/ 500
  grooves /mm today.
• What do you think the benefits of holographic
  diffraction gratings are?

http//www.rit.edu/andpph/exhibit-spectrum.html
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What is a spectrograph?
Fraunhofer lines- Solar Spectrum
http//apod.gsfc.nasa.gov/apod/ap030629.html

• A spectrograph is a tool that allows us to study
  light in a variety of wavelengths. With it, we
  measure the wavelength of incoming light, and
  see which lines appear in a spectrum. A
  spectrograph uses a diffraction grating.

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Spectrograph Uses

• Ground and space-based instrumentation
• In astronomy- helps determine the composition of
  the atmospheres and surfaces of planets, stars,
  and dust
• Engineered to be optimized for different
  wavelengths
• What is the distance between each groove in the
  diffraction grating we will be using today?

www.nasa.gov