Major Concepts of Physics PHY 102 – Lecture #  Syracuse University Lecture #17 Does matter wave? March 30 th Spring 2016 Prof. Liviu Movileanu Room 211, Physics Bldg., Major Concepts of Physics PHY102

Major Concepts of Physics PHY 102 – Lecture #  Syracuse University 1.Review the Bohr model of the hydrogen atom 2. Excitations/Emissions/Ionizations 3. Fluorescence, Phosphorescence, and Chemiluminescence 4. The wave-particle and particle – wave dualities 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 #  Syracuse University The hydrogen atom

Major Concepts of Physics PHY 102 – Lecture #  Syracuse University 4

a 0 = nm Major Concepts of Physics PHY 102 – Lecture #  Syracuse University The hydrogen atom

Ionization  At n = infinity, the energy is zero, and the electron is freed from the proton.  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) - E 1 = 0 – (-13.6) eV = eV. Major Concepts of Physics PHY 102 – Lecture #  Syracuse University

How do we make Polarized Light? II. Reflection - Major Concepts of Physics PHY 102 – Lecture #  Syracuse University

Major Concepts of Physics PHY102 – Lecture #  Syracuse University Electromagnetic waves - Summary

 The Bohr model of hydrogen atom (1913) was the first step, in understanding the unique properties of the energy values for atoms.  It explained the frequencies of light, emitted by hydrogen. Assumptions:  Electron circles the proton. But, only certain discrete values of the radius r are allowed.  Each orbit forms a state.  Bohr’s Key Postulate: These states satisfy:These states satisfy:  L = nh/2π, where n is an integer. n= 1, 2, 3, ….etc.n= 1, 2, 3, ….etc. Here, L = angular momentum = mvr for a circle. v = speed of electron, r = orbit radius.Here, L = angular momentum = mvr for a circle. v = speed of electron, r = orbit radius. Major Concepts of Physics PHY 102 – Lecture #  Syracuse University The Bohr model of the hydrogen atom

Does Matter Wave? 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 = h/mv. Here, v = the particle speed. Can also re-write this relation as: = h/p. Here, p is defined by p = mv, and is called the momentum of the particle. Major Concepts of Physics PHY 102 – Lecture #  Syracuse University

Major Concepts of Physics PHY 102 – Lecture #  Syracuse University

Major Concepts of Physics PHY 102 – Lecture #  Syracuse University Double-slit interference pattern

Major Concepts of Physics PHY 102 – Lecture #  Syracuse University Electron microscope permits a magnification of 50,000 Clostridium butyricum

Major Concepts of Physics PHY102 – Lecture #  Syracuse University Rayleigh’s criterion – limitation by diffraction limit 14

A double-slit experiment Major Concepts of Physics PHY 102 – Lecture #  Syracuse University

Major Concepts of Physics PHY 102 – Lecture #  Syracuse University A double-slit experiment

Major Concepts of Physics PHY 102 – Lecture #  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! Later, precise experiments confirmed the de Broglie relation for. Conclusion Conclusion Duality holds for both matter and radiation. Major Concepts of Physics PHY 102 – Lecture #  Syracuse University

Major Concepts of Physics PHY 102 – Lecture #  Syracuse University The Davisson-Germer experimental set-up Crystalline target

Electron diffraction pattern from a polycrystalline Aluminum sample Major Concepts of Physics PHY 102 – Lecture #  Syracuse University

X-ray diffraction pattern from the same sample Major Concepts of Physics PHY 102 – Lecture #  Syracuse University

Conceptual example 28.1 Major Concepts of Physics PHY 102 – Lecture #  Syracuse University

Major Concepts of Physics PHY102 – Lecture #  Syracuse University Conceptual example 28.1

Major Concepts of Physics PHY 102 – Lecture #  Syracuse University 1.Reading 1.Reading: Chapters 27 th, 28 th Section 27.7: The Bohr model of the hydrogen atom; atomic energy levels, pp (Conceptual examples 27.6, 27.7) Section 28.1 The wave-particle duality, pp Section 28.2 Matter waves, pp (Conceptual example 28.1); Conceptual example Homework. 2. Homework. HW#7 is due on this week’s lab. HW #8, now posted online, is due on the next week’s lab. 3. Workshop this week - Atomic states. Announcements/Reading and homework assignments