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321 Quantum MechanicsUnit 1 Quantum mechanics unit 1 Foundations of QM Photoelectric effect, Compton effect, Matter waves The uncertainty principle The Schrödinger eqn. in 1D Square well potentials and 1D tunnelling The harmonic oscillator Dr Mervyn Roy (S6) www2.le.ac.uk/departments/physics/people/mervynroy/lectures www.le.ac.uk/physics -> people -> Mervyn Roy

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321 Quantum MechanicsUnit 1 Quantum Mechanics, Alastair I. M. Rae Chapters 1 and 2 for unit 1 Physics for scientists and engineers, P. A. Tipler Concepts of modern physics, A. Beiser 114, 214 Course notes Library - Schiff, Mandl etc. www Staff Resources

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321 Quantum MechanicsUnit 1 Classical to Quantum Start of the 19 th century: The importance of QM #1: ~25 years, 9 Nobel prizes Classical - continuous, deterministic Quantum - discrete, probabilistic

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321 Quantum MechanicsUnit 1 The need for a quantum theory 1 Classical theory works well but… UV Catastrophe Photoelectric effect Compton effect …waves as particles

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321 Quantum MechanicsUnit 1 Photoelectric effect Observed by Hertz 1887. Explained by Einstein 1905, Nobel prize 1921

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321 Quantum MechanicsUnit 1 A. H. Compton, Phys. Rev. 21 483 (1923). Nobel prize 1927 Compton effect

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321 Quantum MechanicsUnit 1 The need for a quantum theory 2 Classical theory works well but… Discrete atomic spectra de Broglie waves Electron diffraction …particles as waves

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321 Quantum MechanicsUnit 1 Discrete spectral lines Atoms must have discrete energy levels Bohr, 1913. Nobel prize 1922 The importance of QM #2: Used everywhere in physics – Nano, Space, Planetary, Astrophysics

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321 Quantum MechanicsUnit 1 Matter waves de Broglie hypothesis 1924 - speculated that matter has wave-like character Nobel prize 1929 1927 Experimental evidence Electron diffraction Observed by Davisson and Germer and, independently, by Thomson Nobel prize 1937 (for Davisson and Thomson)

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321 Quantum MechanicsUnit 1 Example Calculate: 1. wavelength of free electron, E = 50 eV 2.wavelength of golf ball, v= 30 ms -1, m=0.046 kg = 0.17 nm = 4.8 x 10 -34 m

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321 Quantum MechanicsUnit 1 C 168 H 94 F 152 O 8 N 4 S 4 (430 atoms) Quantum interference of large organic molecules, S. Gerlich et al, Nature Communications 2 263, 2011 X-rayselectronsneutrons

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321 Quantum MechanicsUnit 1 Probability waves (Born’s postulate 1926, Nobel prize 1954) Electron interference - double slit experiment with electrons

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321 Quantum MechanicsUnit 1 The importance of QM #3: Technology – solid state transistors, e- beam lithography, atomic clocks (GPS), SQUIDs & MRI, Quantum communication/cryptography, Lasers etc. etc. Wave particle duality Light and matter sometimes behave like waves and sometimes like particles – depends on experiment Wave and particle pictures are complementary It is often stated that of all the theories proposed in this century, the silliest is quantum theory. In fact, some say that the only thing that quantum theory has going for it is that it is unquestionably correct. - Michio Kaku, Hyperspace (1995)Michio Kaku

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321 Quantum MechanicsUnit 1 Wave particle duality...the "paradox" is only a conflict between reality and your feeling of what reality "ought to be." Richard Feynman, The Feynman Lectures on Physics, (1965)Richard Feynman What am I? Rae, chapter 13. In Search of Schrödinger’s Cat, John Gribbin

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