lecture 27 - Chapter 27 Quantum Physics Need for Quantum...

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    Chapter 27 Quantum Physics
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    Need for Quantum Physics Problems remained from classical mechanics  that relativity didn’t explain Blackbody Radiation The electromagnetic radiation emitted by a heated  object Photoelectric Effect Emission of electrons by an illuminated metal Spectral Lines Emission of sharp spectral lines by gas atoms in an  electric discharge tube
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    Development of Quantum  Physics 1900 to 1930 Development of ideas of quantum mechanics Also called wave mechanics Highly successful in explaining the behavior of atoms,  molecules, and nuclei Involved a large number of physicists Planck introduced basic ideas Mathematical developments and interpretations  involved such people as Einstein, Bohr, Schrödinger,  de Broglie, Heisenberg, Born and Dirac
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    Blackbody Radiation An object at any temperature emits  electromagnetic radiation Sometimes called  thermal radiation Stefan’s Law describes the total power  radiated The spectrum of the radiation depends on  the temperature and properties of the  object
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    Blackbody Radiation Graph Experimental data for  distribution of energy in  blackbody radiation As the temperature  increases, the total amount  of energy increases Shown by the area under the  curve As the temperature  increases, the peak of the  distribution shifts to shorter  wavelengths
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    Wien’s Displacement Law The wavelength of the peak of the  blackbody distribution was found to  follow  Wein’s Displacement Law λ max  T = 0.2898 x 10 -2  m • K λ max  is the wavelength at which the curve’s  peak T is the absolute temperature of the object  emitting the radiation
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    The Ultraviolet Catastrophe Classical theory did not match  the experimental data At long wavelengths, the match  is good At short wavelengths, classical  theory predicted infinite energy At short wavelengths,  experiment showed no energy This contradiction is called the  ultraviolet catastrophe
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    Planck’s Resolution Planck hypothesized that the blackbody  radiation was produced by  resonators Resonators were submicroscopic charged  oscillators The resonators could only have  discrete  energies E n  = n h ƒ n is called the  quantum number ƒ is the frequency of vibration h is  Planck’s constant , 6.626 x 10 -34  J s Key point is quantized energy states
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    Max Planck 1858 – 1947 Introduced a  “quantum of action,”  h Awarded Nobel  Prize in 1918 for  discovering the  quantized nature of  energy
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    Photoelectric Effect When light is incident on certain metallic 
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This note was uploaded on 09/06/2009 for the course PHYSICS Physics 2A taught by Professor Sydney.sukuta during the Fall '09 term at San Jose City College.

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lecture 27 - Chapter 27 Quantum Physics Need for Quantum...

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