F11Physics1CLec28B

F11Physics1CLec28B - Physics 1C Lecture 28B "In quantum...

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Physics 1C Lecture 28B "In quantum mechanics we have found a region of the universe where the human brain is simply unable to be comfortable." --James Trefil
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Outline Last time: Blackbody radiation - Planck’s solution (1918 Nobel Prize) Photoelectric effect - Einstein’s theory (1921 Nobel Prize) Today: Compton effect (1927 Nobel Prize) Quantum Dots Nature’s Use of Quantum Mechanics
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Quantum Dog Not really quantum small
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Quiz Question Man and mirror – construct rays to see head Reintroduce Quantum Dog
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Quiz Question Dog and mirror – construct rays to see head Construct rays to see feet Test whether it depends on distance
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The Compton Effect In 1923, Arthur Compton (U of Chicago) directed a beam of x-rays toward a block of graphite He detected the scattered x-rays had a slightly longer wavelength than the incident x-rays. This means the scattered photons had less energy than the incident photons. The amount of energy the scattered photons lost depended on the angle at which the x-rays were scattered. This change in wavelength is called the Compton shift (1927 Nobel Prize).
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The Compton Effect To calculate the shift in wavelength, Compton assumed that the photons act like other particles in collisions. In the collisions, energy, hf, and momentum, hf/c , were conserved. The energy of the incoming photon was: After it collides it scatters by an angle θ .
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The Compton Effect 0.00243 e h nm mc After the collision the photon has an energy:
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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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F11Physics1CLec28B - Physics 1C Lecture 28B "In quantum...

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