Lasers Chapter 3 - Lasers PH 645/ OSE 645/ EE 613 Summer...

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Lasers PH 645/ OSE 645/ EE 613 Summer 2010 Section 1: T/Th 2:45- 4:45 PM Engineering Building 240 John D. Williams, Ph.D. Department of Electrical and Computer Engineering 406 Optics Building - UAHuntsville, Huntsville, AL 35899 Ph. (256) 824-2898 email: williams@eng.uah.edu Office Hours: Tues/Thurs 2-3PM JDW, ECE Summer 2010
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Chapter 3: The Particle Nature of Light Bohr Theory of the Hydrogen Atom Quantum Theory of Atomic Energy Levels Angular Momentum of Atoms Energy Levels Associated with One- Electron Atoms Periodic Table of the Elements Energy Levels of Multi-Electron Atoms Cambridge University Press, 2004 ISBN-13: 9780521541053 All figures presented from this point on were taken directly from (unless otherwise cited): W.T. Silfvast, laser Fundamentals 2 nd ed., Cambridge University Press, 2004. Chapter 3 Homework: 1, 2, 5, 6, 10, 13, 14
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Problems with the Classical View Photoelectric Effect: The flux of photoelectrons emitted from a surface depends on the incident intensity, however the kinetic energy said electrons is independent of intensity. How does one compensate for the energy emitted? Secondly, how does one explain the sharp threshold wavelength of the incident light required to generate photoemission? Fraunhofer Lines: Dark bands isolating narrow emission lines present in chemical spectra of gases, and stellar observations. What is it about chemical species that requires a specific wavelength emission? http://en.wikipedia.org/wiki/Fraunhofer_lines
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Bohr Model Niels Bohr attempted to explain these anomalies in 1913 through a model designed to characterize the emission spectrum from the gas discharge of the hydrogen atom Physicist at the time had already discovered the size, charge, and mass of the electron as using the Zeeman effect which showed a splitting of the spectral line widths present in an emission spectrum under the presence of a strong magnetic field. However, there was no model predicting how the spectral lines were generated in the first place. Bohr proposed the following hypotheses in attempt to explain these lines 1. The H atom included a positively charged nucleus and a negatively charged electron orbiting in a circular motion 2. The electron could orbited in closed circular orbital's based on the amount of angular momentum of the electron and that each state was an integral multiplier of Plank’s constant , h, divided by 2 π 3. Because the orbits are “quantized” in radius by Plank’s constant, the electron must lose and gain a quantized amount of energy when it moves from one orbit to the next. 4. The radiation emitted or absorbed during when an electron moves from one orbit (or state) to another is determined by the Einstein frequency condition
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Bohr Model Continued Using the spectral line widths experimentally determined by others, Bohr was able to predict the various states of the H atom by assuming that an electron with velocity, v, rotates in a circular orbit of radius r around the nucleus. Notice that this model is essentially classical in nature with the two additional assumptions
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Lasers Chapter 3 - Lasers PH 645/ OSE 645/ EE 613 Summer...

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