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# l8 - Classical and quantum light Compton scattering X rays...

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Unformatted text preview: Classical and quantum light Compton scattering X rays Röntgen Use and abuse X-ray diffraction von Laue Bragg diffraction Generating X rays Protein crystallography Forces: q and m The electron Plum pudding Electron charge Radioactivity Rutherford Next week • No lecture on Tuesday! The University follows a Monday class schedule, and I’ll be in Australia besides. • No labs next week! • No recitations next Wednesday, Sep. 30. Available by Skype ( cjjxray ) on Wednesday 16:15-17:00, and by email. • Thursday, October 1: Exam 1 in this room. You’ll get the exam, blue books, and an equation sheet. All you can have on your desk is a pen or pencil, and a calculator. • Exam will cover Serway chapters 1–3, and homeworks 1–3. Classical and quantum light Compton scattering X rays Röntgen Use and abuse X-ray diffraction von Laue Bragg diffraction Generating X rays Protein crystallography Forces: q and m The electron Plum pudding Electron charge Radioactivity Rutherford Classical light The classical picture of light is as an electromagnetic wave. • Interference and diffraction • ( E ) ∝ √ I where ( E ) is the time-averaged mean electric field, and I is the irradiance (Watts/m 2 ). • Rayleigh scattering: scattered light at same frequency as incident light, scattering strength proportional to ν 4 (or ω 4 or λ − 4 ). Einstein: “The wave theory of light, which operates with continuous spatial functions, has proved itself splendidly in describing purely optical phenomena and will probably never be replaced by another theory. One should keep in mind, however, that optical observations apply to time averages and not to momentary values . . . ” Classical and quantum light Compton scattering X rays Röntgen Use and abuse X-ray diffraction von Laue Bragg diffraction Generating X rays Protein crystallography Forces: q and m The electron Plum pudding Electron charge Radioactivity Rutherford Quantum and relativistic light Planck finds E = nh ν explains the blackbody spectrum, and Einstein takes Planck at his word! • Photon: quantum of light energy. Photon energy is E = h ν = hc /λ • Photons carry momentum of p = E / c • Photons arriving one-by-one land at particular points, yet accumulate into the pattern predicted by wave interference. Thus photons interfere with themselves! • Photoelectric effect explained by K = h ν − ϕ , where K is the kinetic energy of the ejected electron and ϕ is the work function of the metal. Radical picture, but it explains all observations! Classical and quantum light Compton scattering X rays Röntgen Use and abuse X-ray diffraction von Laue Bragg diffraction Generating X rays Protein crystallography Forces: q and m The electron Plum pudding Electron charge Radioactivity Rutherford The Compton effect • Photon collides with an electron (initially at rest)....
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l8 - Classical and quantum light Compton scattering X rays...

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