10/19/20111The Nature of Light SunTools of AstronomyElectromagnetic SpectrumSpectrumContinuous Spectrum• From glowing gas under pressure• Like the interior of SunDark Line Spectrum• White light passing through cold, low pressure gas• Gas absorbs its elemental wavelength signature10/19/20112Bright Line Spectrum• Incandescent hot gas emits its elemental wavelength signature3 types of spectraHow much of the electromagnetic spectrum is visible light?25% 25%25%25%1. All of it2. Most of it3. Only a tiny 1234fraction4. None of itSunPhoto of Sun’s granular surface Detail of Sunspot10/19/20113Group of SunspotsSunspot Variation over timeSpicules of the Chromosphere Solar CoronaSolar wind blows comet tailshttp://www.astro.uva.nl/demo/sun/inter.htmSolar Prominencehttp://antwrp.gsfc.nasa.gov/apod/image/0109/sunplume_soho_big.gifVideo clip http://antwrp.gsfc.nasa.gov/apod/ap030223.htmlAnother video clip http://spacescience.com/headlines/images/prominence/prominence_10jan00.mov10/19/20114Auroras Aurora photo from Skylabhttp://www.astro.uva.nl/demo/sun/aarde.htmSurface Detail of Sun Solar Interior• Nuclear Fusion of 4 Hydrogen to 1 Helium• Difference in atomic mass is released as energyRl d hli h il•Released as photons—light particles• Convection brings photons to photosphere• Sun will last about another 5 billion yearsStructure of SunSun Structure• Photosphere: most visible part— “Surface”– Hydrogen and helium– Granules, sunspots• Chromosphere: lower atmosphere– Spicules from granules of photosphere–prominencesprominences• Corona: outer atmosphere– Ionized gases– Solar wind• Solar flares– Create auroras– Associated with sunspots10/19/20115Sun now and laterThis page was copied from Nick Strobel's Astronomy Notes. Go to his site at www.astronomynotes.com for the updated and corrected version Red Giant BetelgeuseThis page was copied from Nick Strobel's Astronomy Notes. Go to his site at www.astronomynotes.com for the updated and corrected version Nebula—eventual Sunhttp://www.astro.uva.nl/demo/sun/leven.htmMain Sequence to Red Giant to White Dwarfhttp://imagine.gsfc.nasa.gov/docs/science/know_l2/dwarfs.htmlThe Nature of Light• Light is made of photons• Photons act as particles• Photons act as wavesWaves• Movement of energy, not of matter10/19/20116Overlapping ripplesWaves are movement of energy• The matter pretty much stays putuc stays put• Video link below, clip #142‐69http://www.4oliveus.com/land_4_sale/images/L_Wave_of_Grass.jpghttp://creative.gettyimages.com/source/frontdoor/DefaultFilm.aspxTrace of pendulum Wave terminologyhttp://cimss.ssec.wisc.edu/satmet/modules/spectrum/wavelength.htmlWave Description• Wavelength—distance from one part of the wave to the same part of the next wave• Crest—top•Trough—bottomTroughbottom• Amplitude—distance from midway between crest and trough, to the crest or trough• Period—time for one complete wave to pass• Frequency—how often the wave passesElectromagnetic Spectrum10/19/20117Rippleshttp://www.yenra.com/banner‐ad‐effectiveness/Stationary BugMoving Bug Doppler Effect of Siren• Doppler effect of a whistle in the youtube linkhttp://www.youtube.com/watch?v=NvBvTuOxU‐0Doppler effect of movement on the reception of wave formsEffect of Red Shift on Na
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