PHY213_Chapter27_Sec1to3

PHY213_Chapter27_Sec1to3 - Chapter 27 Quantum Physics...

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Chapter 27 Quantum Physics
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General Physics Quantum Physics I Sections 1–3
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General Physics Need for Quantum Physics Other problems remained in classical physics which relativity did not explain Blackbody Radiation The electromagnetic radiation emitted by a heated object Photoelectric Effect Emission of electrons by an illuminated metal Compton Effect A beam of x-rays directed toward a block of graphite scattered at a slightly longer wavelength Spectral Lines Emission of sharp spectral lines by gas atoms in an electric discharge tube
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General Physics Development of Quantum Physics Beginning in 1900 Development of ideas of quantum physics • Also called wave mechanics • Highly successful in explaining the behavior of atoms, molecules, and nuclei Involved a large number of physicists
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General Physics 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 4 T Power
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General Physics 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 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 Active Figure: Blackbody Radiation
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General Physics 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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General Physics
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This note was uploaded on 08/25/2009 for the course PHY 213 taught by Professor Cao during the Summer '08 term at Kentucky.

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PHY213_Chapter27_Sec1to3 - Chapter 27 Quantum Physics...

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