11Announcements Astronomy 101A 10/05/11 Jacobsen Observatory 8:30 - 9:30 pm OPTIONAL(especially if it is not clear) Review for exam 1 on Friday; exam 1 Monday, 10/10– Will have summer’s exam on-line soon (willannounce) for study purposes– Mix of short answers, fill in blanks, short essay,reading star map, vocabulary Exercise on spectral analysis in sections tomorrow -important for next 2 weeks! (and, your scores)2Wavelength (meters)3If we could see at IR wavelengths, what would we see?Radio wavesInfrared RadiationMicrowaves24Ultraviolet A, B, CX-RaysGamma RaysThe Sun’s UV rays can cause: * More wrinkles * Sagging skin * Age or liver spots * Tan/sunburn * Eye damage/ cataracts * Skin Cancer5Messier 82 (M82)opticalinfraredColor Coded:Blue - x-rayRed - opticalGreen -wavelength = 3 mmCO molecule (H2)6o Define light (electromagnetic radiation) anddescribe how we characterize ito List 3 ways that light is createdo Explain why stars appear to be different colorsand how we use this propertyo Distinguish between emission and absorptionspectra by what is happening with the electron inthe atom.Learning goals37o Define light (electromagnetic radiation) anddescribe how we characterize ito List 3 ways that light is createdo Explain why stars appear to be different colors and how we use thispropertyo Distinguish between emission and absorption spectra by what ishappening with the electron in the atom.Learning goals8Light measured in wavelength λ, frequency ν,or photon energy; light has the velocity c in avacuumWhy are outer ends “black”? Define light (electromagnetic radiation) and describe how we characterize it9Light can behave as a wave OR a PARTICLE!E = hν[Planck’s Constant:EnergyFrequency (nu)RODS &CONES410•Oscillation of electric andmagnetic fields•Propagates through spaceand some materialsElectromagnetic Radiation:o- blackbody radiation (thermal)o- emission as electrons lose energy in an atomo- electrons spiraling in a magnetic fieldProduced By: Define light (electromagnetic radiation) and describe how we characterize it List 3 ways that light is created (astronomically speaking)11o Define light (electromagnetic radiation) and describe how wecharacterize ito List 3 ways that light is created.12o Define light (electromagnetic radiation) and describe how we characterize ito List 3 ways that light is createdo Explain why stars appear to be different colorsand how we use this propertyo Distinguish between emission and absorption spectra by what is happening with theelectron in the atom.Learning goalsPlease take out a full sheet of paper, and putyour name, and section (or TA’s name) atthe top. Unannounced participation activity!513Continuous Spectrum - created by thermal radiator(blackbody radiation)Hotter stars look more blue-white thancooler stars because hot stars emit mostof their light at shorter wavelengths.! "peak=2.9 # 106T nmT = 2.9 # 106"peakKWien’s LawStar field in Sagittarius Explain why stars appear to be different colors and how we use this property14Tutorial: BlackbodyRadiationViolet, green/yellow, red; very little blue or yellow/orange.a)15Stars A & BStars A & BCWhen objects emit light over all wavelengths, they look white, so star Awill be whitish. Star C is emitting loght mostly in yellow/red, so will look“redder.”616Different surface temperatures1718719o Define light (electromagnetic radiation) and describe how we characterize ito List 3 ways that light is createdo Explain why stars appear to be different colors and how we use this propertyo Distinguish between emission and absorption spectraby what is happening with the electron in the atom.Learning goals20Physical processes behind emission and absorptionby atoms (representation of hydrogen energy levels):123456Energy level21 Distinguish between emission and absorption spectra by what is happening with the electronin the atom.822 Distinguish between emission and absorption spectra by what is happening with the electronin the atom.23Idealized Realistic Distinguish between emission and absorption spectra by what is happening with the electronin the atom.24Emission vs absorption
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