1. Spectrographs

2. 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_grating

3. 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

4. What is a spectrograph? 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. Fraunhofer lines- Solar Spectrum http://apod.gsfc.nasa.gov/apod/ap030629.html

5. 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