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What is light? Light as an electromagnetic wave Light as a particle, the photon Phys 1970B Introductory Optics Brown University Lecture by Rudolf Oldenbourg 4 February 2009
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electromagnetic field the current i increases the charge on the condenser plates the increasing charge increases the electric field E between the plates the increasing E -field generates a magnetic field B the current i also generates a B field around the wire In this example the E-field is generated by charges on the condenser plates In the next example of an oscillating dipole we will find that time varying E and B fields can sustain themselves in the form of an electromagnetic wave
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electric field of an oscillating dipole
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the far field of an oscillating dipole is an electromagnetic wave characteristics: amplitude, frequency, phase, wavelength, speed
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wavelength
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Sources of light thermal or black body radiation accelerating charge chemical reactions excited atoms, molecules
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Thermal radiation Random motion of atoms I black body
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Synchrotron radiation DESY Hamburg, Germany National Synchrotron Lightsource, Brookhaven NY
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Aurora
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Fluorescent light bulb
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Atomic excitation
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Frauenhofer lines
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Fluorescence fluorescein molecule single molecule fluorescence
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light is a particle
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photon counting photon counting noise
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photon counting
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Bibliography Many images are taken from the book by E. Hecht, Optics, Addison-Wesley, 4th edition Other sources: http://www.andor.com/learning/light/ http://en.wikipedia.org/wiki/Thermodynamic_temperature http://zms.desy.de/index_eng.html http://en.wikipedia.org/wiki/File:Polarlicht_2.jpg http://sdsu-physics.org/physics180/physics180B/p180b_images/fluorescent_lit.jpg http://hesperia.gsfc.nasa.gov/~jma/thesis/online/node1.html
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