28A blackbody,planck

28A blackbody,planck - 5/11/2011 Outline Physics 1C Lecture...

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5/11/2011 1 Physics 1C Lecture 28A Science cannot solve the ultimate mystery of nature. And that is because, in the last analysis, we ourselves are a part of the mystery that we are trying to solve. --Max Planck Outline Early foundation for quantum mechanics Blackbody radiation Planck’s solution (1918 Nobel Prize) Quantum oscillator Photoelectric effect Einstein’s theory (1921 Nobel Prize) Blackbody Radiation An object at any temperature emits electromagnetic radiation (also called thermal radiation ). Stefan’s Law describes the total power radiated at all wavelengths: P = A σ T 4 s = 5.670x10 -8 W m -2 K 4 - Stefan-Boltzman constant. The spectrum of radiation depends on the temperature and properties of the object. As the temperature increases, the peak of the intensity shifts to shorter wavelengths. Blackbody Radiation A blackbody is any body that is a perfect absorber or emitter of light. The wavelength of the peak of the blackbody distribution was found to follow Wien’s Displacement Law: λ max T = 2.898 x 10 -3 m K where λ max is the wavelength at which the curves peak T is the absolute temperature of the object emitting the radiation. The wavelength is inversely proportional to the absolute temperature. As T increases, the peak is “displaced” to shorter l . Blackbody Approximation A good approximation of a black body is a small hole leading to the inside of a hollow object. The nature of the radiation leaving the cavity through the hole depends only on the temperature of the cavity walls. Thermal radiation
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This note was uploaded on 02/11/2012 for the course PHYS 1C 1C taught by Professor Wethien during the Spring '11 term at UCSD.

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28A blackbody,planck - 5/11/2011 Outline Physics 1C Lecture...

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