Astr. 101 Notes 5

Astr. 101 Notes 5 - -energy of photons(energy is...

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-energy of photons (energy is quantized)-energy of one photon of a specific color (wavelength) is E=hc/lambda, v=c/lambda, E=hv where h is Planck’s constant (6.625 x 10^-34 J/s); an electron changing energy levels in one atom is the result of one photon being emitted, or one photon being absorbed -concave vs. convex-most refractors use convex lenses but achromat doublets are a combo of a convex objective and a concave corrector lens; Newtonian telescopes use a flat diagonal mirror near the entrance of the telescope tube; Cassegrain telescopes use a concave objective (primary) mirror and a convex secondary mirror near the prime focus -concave-curves inward -convex-curves outward -problems w/ adaptive optics-need to use bright star very close to observed target and a good stable atmosphere; seeing is typically less on mountain tops but it does vary; there is also a limit to the speed, computing power, and number of variations which can be applied to the flexible mirror to attempt to correct the atmospheric distortion -laser guide stars-still limited in atmospheric conditions (incomplete correction and clouds; even thin haze will shut down LGS systems; must turn off when planes and some military satellites go by) -light pollution-from cities; while we try to get away from light pollution on mountain tops, the light bounces off molecules and particles in our atmosphere and it still gets there -Hubble space telescope-get away from factors like light pollution -CDEs and color images-photographic film, and then electronic detectors allow astronomers to “integrate” light over time and look for fainter emission to build up over that “integration time” -grating spectrograph-separate out/ add colors to an image -Parkes 64m Radio Telescope-resolution at 5cm; radio telescopes are just like optical Price Focus and Cassegrain telescopes but tend to have very short focal lengths; smooth to a radio wave is much more rough than smooth to a visible light wave (small fraction of wavelength) -interferometry-take light from multiple telescopes, put that light together (Very Large Array) -Spitzer Space Telescope-infrared, must be cooled so the blackbody radiation of the telescopes is much
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This note was uploaded on 05/13/2011 for the course ASTR 101 taught by Professor Christiansen during the Spring '08 term at UNC.

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Astr. 101 Notes 5 - -energy of photons(energy is...

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