Nano Science (Lec5 Quantum mechanics)

Nano Science (Lec5 Quantum mechanics) - MAE 287/EE 257 1 It...

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MAE 287/EE 257 1
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It seems Newton’s law can be applied to everything, from an apple to stars… 2
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Naturally we expected that the Newton’s law can be applied to objectives as small as atoms, molecules in the nanoworld… 3
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This was a perplexing results: Most people continue to imagine electron to be a unimaginably small particle, the diffraction pattern can only observed when the electron interferes with itself when it passes through the slit, but that idea is strongly at odds with the truism, "You cannot be two places at once." If a particle is conceptualized as a wave, but what kind of wave it is? In the electron diffraction experiment, the electron gun on the left shoots electrons, and some of the electrons passes through a double slit barrier and reaches to the wall. The wall registers the positions of the electrons. The diffraction pattern shows the particle has wave character. 5
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The diffraction pattern of electrons can be directly observed by TEM and other characterization techniques when the electronic beam pass through a crystal with a periodic structures. 6
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The forms of the electric and magnetic fields as a wave moving in k - direction are where f is the frequency and k= 2 p / l is the wave vector. They are related by w /k = c/n, where c is the speed of light in vacuum, n is the refraction index of the media )] r - t ( Exp[ t) , r ( )] r - t ( Exp[ t) , r ( 0 0 k i H H k i E E y x 7
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James Clerk Maxwell (1831 - 1879) Electromagnetic waves follow Maxwell's Equations 0 0 - 0 0 H E t H E t E H 8
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In 1902, Philipp Lenard made the first quantitative measurements of the photoelectric effect. He used a bright light to study how the energy of the emitted photoelectrons varied with the intensity of the light and, by separating out individual colors, with the frequency of light. Increasing the frequency of light, by selecting light from the bluer end of the spectrum, caused the ejected electrons on average to be more energetic, as predicted. Increasing the intensity of light caused more electrons to be thrown out, also as expected. On the other hand, increasing the intensity with certain low-energy light had no effect at all on the average amount of energy that each ejected electron carried away. That came as a real shock. If, as
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Nano Science (Lec5 Quantum mechanics) - MAE 287/EE 257 1 It...

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