28C quantum mech

28C quantum mech - Outline Physics 1C Lecture 28B...

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5/20/2011 1 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 Outline Wave-particle duality Electron diffraction The Uncertainty Principle Quiz-like Question Dog and mirror – construct rays to see head Construct rays to see feet Test whether it depends on distance Wave Particle Duality Experiments such as the photoelectric effect, the Compton effect, and double-slit interference helped to describe light’s true nature: a wave and a particle. Light has a dual nature, exhibiting both wave and particle characteristics. This means a photon can have energy given by: And that photons can have a momentum given by: or l = h/p Wave Particle Duality Then in 1923, Louis de Broglie (Sorbonne, Paris) proposed a very interesting hypothesis: Because photons have wave and particle characteristics, perhaps all forms of matter have both properties. de Broglie proposed that subatomic particles, like protons and electrons, will have wavelengths just like photons. de Broglie suggested that a particle of mass m and velocity v would have a wavelength of: This is known as the de Broglie wavelength of a particle. hh p mv l  Wave Particle Duality de Broglie also postulated that matter waves have frequencies that can be found as: But de Broglie only hypothesized about matter waves, what kind of experiment could we design to demonstrate the wave nature of particles (like electrons)? We could shoot electrons through a double slit apparatus and observe if there is a resulting interference pattern (similar to the pattern we observed for light).
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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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28C quantum mech - Outline Physics 1C Lecture 28B...

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