Copyright © 2009 Pearson Education, Inc.Midterm #1• Wednesday 01 Oct 2009• Chapters 1-4• Bring Scantron page + #2 pencil to throw atthe teacher• Will not take the full period• RelaxCopyright © 2009 Pearson Education, Inc.++--Copyright © 2009 Pearson Education, Inc.Chapter 5Light: The Cosmic MessengerCopyright © 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
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