1. Major Concepts of Physics PHY 102 – Lecture #17 1 2016  Syracuse University Lecture #17 Does matter wave? March 30 th Spring 2016 Prof. Liviu Movileanu lmovilea@syr.edu Room 211, Physics Bldg., 443-8078 Major Concepts of Physics PHY102

2. Major Concepts of Physics PHY 102 – Lecture #17 2 2016  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

3. Major Concepts of Physics PHY 102 – Lecture #17 3 2016  Syracuse University The hydrogen atom

4. Major Concepts of Physics PHY 102 – Lecture #172016  Syracuse University 4

5. a 0 = 0.0529 nm Major Concepts of Physics PHY 102 – Lecture #17 5 2016  Syracuse University The hydrogen atom

6. 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 = +13.6 eV. Major Concepts of Physics PHY 102 – Lecture #17 6 2016  Syracuse University

7. How do we make Polarized Light? II. Reflection - Major Concepts of Physics PHY 102 – Lecture #17 7 2016  Syracuse University

8. Major Concepts of Physics PHY102 – Lecture #17 8 2016  Syracuse University Electromagnetic waves - Summary

9.  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 #17 9 2016  Syracuse University The Bohr model of the hydrogen atom

10. 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 #17 10 2016  Syracuse University

11. Major Concepts of Physics PHY 102 – Lecture #17 11 2016  Syracuse University

12. Major Concepts of Physics PHY 102 – Lecture #17 12 2016  Syracuse University Double-slit interference pattern

13. Major Concepts of Physics PHY 102 – Lecture #17 13 2016  Syracuse University Electron microscope permits a magnification of 50,000 Clostridium butyricum

14. Major Concepts of Physics PHY102 – Lecture #172016  Syracuse University Rayleigh’s criterion – limitation by diffraction limit 14

15. A double-slit experiment Major Concepts of Physics PHY 102 – Lecture #17 15 2016  Syracuse University

16. Major Concepts of Physics PHY 102 – Lecture #17 16 2016  Syracuse University A double-slit experiment

17. Major Concepts of Physics PHY 102 – Lecture #17 17 2017  Syracuse University A double-slit experiment

18. 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 #17 18 2016  Syracuse University

19. Major Concepts of Physics PHY 102 – Lecture #17 19 2016  Syracuse University The Davisson-Germer experimental set-up Crystalline target

20. Electron diffraction pattern from a polycrystalline Aluminum sample Major Concepts of Physics PHY 102 – Lecture #17 21 2016  Syracuse University

21. X-ray diffraction pattern from the same sample Major Concepts of Physics PHY 102 – Lecture #17 21 2017  Syracuse University

22. Conceptual example 28.1 Major Concepts of Physics PHY 102 – Lecture #17 22 2016  Syracuse University

23. Major Concepts of Physics PHY102 – Lecture #17 23 2016  Syracuse University Conceptual example 28.1

24. Major Concepts of Physics PHY 102 – Lecture #17 24 2016  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. 1023-1025 (Conceptual examples 27.6, 27.7) Section 28.1 The wave-particle duality, pp. 1041-1042 Section 28.2 Matter waves, pp. 1042-1043 (Conceptual example 28.1); Conceptual example 28.1 2. 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