Major Concepts of Physics PHY 102 – Lecture #17: Quantum Mechanics (II) and Matter Waves -, Study notes of Physics

Download Major Concepts of Physics PHY 102 – Lecture #17: Quantum Mechanics (II) and Matter Waves - and more Study notes Physics in PDF only on Docsity! 1 Major Concepts of Physics PHY 102 – Lecture #17 12009Syracuse University Lecture #17 Quantum mechanics (II) March 25th Spring 2009 Prof. Liviu Movileanu http://physics.syr.edu/courses/PHY102.07Spring/index.html lmovilea@physics.syr.edu Room 211, Physics Bldg., 443-8078 Major Concepts of Physics PHY102 Major Concepts of Physics PHY 102 – Lecture #17 22009Syracuse University 1. Review the Bohr model of the hydrogen atom 2. Excitations/Emissions/Ionizations 3. Fluorescence, Phosphorescence, and Chemiluminescence 4. The wave-particle duality 5. Matter waves. De Broglie hypothesis Experimental demo (The diffraction of electrons) 6. Conceptual example – Electron diffraction experiment Lecture objectives Major Concepts of Physics PHY 102 – Lecture #17 32009Syracuse University The hydrogen atom 2 Major Concepts of Physics PHY 102 – Lecture #16 2009Syracuse University 4 Major Concepts of Physics PHY 102 – Lecture #17 52009Syracuse University The hydrogen atom Ionization At n = infinity, the energy is zero, and the electron is freed from the proton. • The ionization energy (also called the binding energy) is defined as the energy to liberate the electron, if the system is initially in its ground state. • So, for hydrogen, the ionization energy is • E (at infinity) - E1 = 0 – (-13.6) eV = +13.6 eV. Major Concepts of Physics PHY 102 – Lecture #17 62009Syracuse University 5 Matter Waves: The Wave Nature of Matter Louis de Broglie (1923) proposed that particles also have duality. They can behave like a wave, or like a particle. He proposed: All particles also have a wavelength . This wavelength displays the wave-aspects. He postulated that the value of the wavelength is λ = h/mv. Here, v = the particle speed. Can also re-write this relation as: λ = h/p. Here, p is defined by p = mv, and is called the momentum of the particle. Major Concepts of Physics PHY 102 – Lecture #17 132009Syracuse University Major Concepts of Physics PHY 102 – Lecture #16 142009Syracuse University A double-slit experiment Major Concepts of Physics PHY 102 – Lecture #17 152009Syracuse University 6 Major Concepts of Physics PHY 102 – Lecture #17 162009Syracuse University A double-slit experiment Major Concepts of Physics PHY 102 – Lecture #17 172009Syracuse University A double-slit experiment Experimental Confirmation Electron diffraction was observed in 1925 by Davisson and Germer. A crystal served to diffract the electrons. No explanation, but this: Matter waves exist! Do electron diffraction demo. Later, precise experiments confirmed the de Broglie relation for . Conclusion Duality holds for both matter and radiation. Major Concepts of Physics PHY 102 – Lecture #17 182009Syracuse University 7 Major Concepts of Physics PHY 102 – Lecture #17 192009Syracuse University The Davisson-Germer experimental set-up Electron diffraction pattern from a polycrystalline Aluminum sample Major Concepts of Physics PHY 102 – Lecture #17 202009Syracuse University X-ray diffraction pattern from the same sample Major Concepts of Physics PHY 102 – Lecture #17 212009Syracuse University