Copyright © 2009 Pearson Education, Inc.Chapter 5Light: The Cosmic MessengerCopyright © 2009 Pearson Education, Inc.What is the Budget of the US?A. $500BB. $3 TrillionC. $15 TrillionD. $100 TrillonCopyright © 2009 Pearson Education, Inc.Copyright © 2009 Pearson Education, Inc.What is the NASA budget?A. $2BB. $20BC. $50BD. $100BCopyright © 2009 Pearson Education, Inc.Copyright © 2009 Pearson Education, Inc.What is the DOD budget?A. $50BB. $200BC. $500BD. $1TCopyright © 2009 Pearson Education, Inc.DOD budget - $500B~(?)$6B for satellitesCopyright © 2009 Pearson Education, Inc.What is the NSF budget?A. $2BB. $20BC. $200BCopyright © 2009 Pearson Education, Inc.Copyright © 2009 Pearson Education, Inc.How much do we spend onastronomy?A. $200MB. $1.5BC. $5BD. $20BCopyright © 2009 Pearson Education, Inc.Astronomy Budget• NSF $250M <==• DOE $100M <==• NASA– $1.3B Astrophysics <==– $1.4B Mission to Planet Earth– $0.5B Heliophysics– $1.3B PlanetaryCopyright © 2009 Pearson Education, Inc.NASA AstrophysicsSubcommittee MeetingCopyright © 2009 Pearson Education, Inc.5.1 Basic Properties of Light and MatterOur goals for learning:• What is light?• What is matter?• How do light and matter interact?Copyright © 2009 Pearson Education, Inc.What is light?Copyright © 2009 Pearson Education, Inc.Copyright © 2009 Pearson Education, Inc.Light is anelectromagnetic wave.Copyright © 2009 Pearson Education, Inc.Anatomy of a WaveCopyright © 2009 Pearson Education, Inc.Wavelength and Frequencywavelength ! frequency = speed of light = constantCopyright © 2009 Pearson Education, Inc.The Electromagnetic SpectrumElectromagnetic SpectrumCopyright © 2009 Pearson Education, Inc.Particles of Light• Particles of light are called photons.• Each photon has a wavelength and afrequency.• The energy of a photon depends on itsfrequency.Copyright © 2009 Pearson Education, Inc.Wavelength, Frequency, and Energy l ! f = cl = wavelength, f = frequencyc = 3.00 ! 108 m/s = speed of lightE = h ! f = photon energyh = 6.626 ! 10-34 joule ! s = photon energyCopyright © 2009 Pearson Education, Inc.Thought QuestionThe higher the photon energy,A. the longer its wavelength.B. the shorter its wavelength.C. Energy is independent of wavelength.Copyright © 2009 Pearson Education, Inc.Thought QuestionThe higher the photon energy,A. the longer its wavelength.B. the shorter its wavelength.C. Energy is independent of wavelength.Copyright © 2009 Pearson Education, Inc.What is matter?Copyright © 2009 Pearson Education, Inc.Atomic Terminology• Atomic Number = # of protons in nucleus• Atomic Mass Number = # of protons + neutronsCopyright © 2009 Pearson Education, Inc.Atomic Terminology• Isotope: same # ofprotons but different# of neutrons (4He,3He)• Molecules:consist of two ormore atoms(H2O, CO2)Copyright © 2009 Pearson Education, Inc.How do light and matter interact?• Emission• Absorption• Transmission— Transparent objects transmit light.— Opaque objects block (absorb) light.• Reflection or scatteringCopyright © 2009 Pearson Education, Inc.Reflection and ScatteringMirror reflects lightin a particulardirection.Movie screen scatters lightin all directions.Copyright © 2009 Pearson Education, Inc.Interactions of Light with MatterInteractions between light and matter determine theappearance of everything around us.Copyright © 2009 Pearson Education, Inc.Thought QuestionWhy is a rose red?A. The rose absorbs red light.B. The rose transmits red light.C. The rose emits red light.D. The rose reflects red light.Copyright © 2009 Pearson Education, Inc.Thought QuestionWhy is a rose red?A. The rose absorbs red light.B. The rose transmits red light.C. The rose emits red light.D. The rose reflects red light.Copyright © 2009 Pearson Education, Inc.What have we learned?• What is light?— Light is a form of energy.— Light comes in many colors that combine to formwhite light.— Light is an electromagnetic wave that also comes inindividual “pieces” called photons. Each photon hasa precise wavelength, frequency, and energy.— Forms of light are radio waves, microwaves,infrared, visible light, ultraviolet, X rays, and gammarays.• What is matter?— Ordinary matter is made of atoms, which are made ofprotons, neutrons, and electrons.Copyright © 2009 Pearson Education, Inc.What have we learned?• How do light and matter interact?—Matter can emit light, absorb light, transmitlight, and reflect (or scatter) light.—Interactions between light and matterdetermine the appearance of everything wesee.Copyright © 2009 Pearson Education, Inc.5.2 Learning from LightOur goals for learning:• What are the three basic types of spectra?• How does light tell us what things are madeof?• How does light tell us the temperatures ofplanets and stars?• How does light tell us the speed of a distantobject?Copyright © 2009 Pearson Education, Inc.What are the three basic types ofspectra?Continuous SpectrumEmission Line SpectrumAbsorption Line SpectrumSpectra of astrophysical objects are usually combinations ofthese three basic types.Copyright © 2009 Pearson Education, Inc.Introduction to SpectroscopyCopyright © 2009 Pearson Education, Inc.Three Types of SpectraIllustrating Kirchhof's LawsCopyright © 2009 Pearson Education, Inc.Continuous Spectrum• The spectrum of a common (incandescent) lightbulb spans all visible wavelengths, withoutinterruption.Copyright © 2009 Pearson Education, Inc.Emission Line Spectrum• A thin or low-density cloud of gas emits light only atspecific wavelengths that depend on its composition andtemperature, producing a spectrum with bright emissionlines.Copyright © 2009 Pearson Education, Inc.Absorption Line Spectrum• A cloud of gas between us and a light bulb can absorb lightof specific wavelengths, leaving dark absorption lines inthe spectrum.Copyright © 2009 Pearson Education, Inc.How does light tell us whatthings are made of?Spectrum of the SunCopyright © 2009 Pearson Education, Inc.Chemical Fingerprints• Each type of atomhas a unique set ofenergy levels.• Each transitioncorresponds to aunique photonenergy, frequency,and wavelength.Energy levels of hydrogenCopyright © 2009 Pearson Education, Inc.Chemical Fingerprints• Downwardtransitions producea unique pattern ofemission lines.Copyright © 2009 Pearson Education, Inc.Production of Emission LinesCopyright © 2009 Pearson Education, Inc.Chemical Fingerprints• Because those atomscan absorb
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