F11Physics1CLec28A

F11Physics1CLec28A - Physics 1C Lecture 28A Science cannot...

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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
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Quiz 3 Results Average 76 Standard deviation 17 Will Post later today
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Outline Early foundation for quantum mechanics Blackbody radiation Planck’s solution (1918 Nobel Prize) Quantum oscillator Photoelectric effect Einstein’s theory (1921 Nobel Prize)
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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.
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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 .
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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 from the human body: T = 36.6ºC, λ max = 9.8μm.
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Blackbody Radiation The experimental data of the emitted blackbody radiation did not match with what classical theory predicted. Classical theory
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This note was uploaded on 12/11/2011 for the course PHYS 1C taught by Professor Smith during the Fall '07 term at UCSD.

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F11Physics1CLec28A - Physics 1C Lecture 28A Science cannot...

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