Download ISP209s8 Lecture 14: Electromagnetic Waves and Quantum Mechanics and more Assignments Physical Education and Motor Learning in PDF only on Docsity! ISP209s8 Lecture 14 -1- Today • Announcements: – HW#7 is due after Spring Break on Wednesday March 12th – Exam #2 is on Thursday after Spring Break – The fourth extra credit project will be a “super bonus” points project. This extra credit can let your homework score go over 100% • Light • Wave-particle duality of nature • Quantum Mechanics ISP209s8 Lecture 14 -2- The Electromagnetic Spectrum • Maxwell’s 4 equations describe the unity of electric and magnetic forces. • They predict an electromagnetic wave that travels at the speed of c (3.00E+8 m/s) ISP209s8 Lecture 14 -5- What is Light? • Wave Picture – oscillating electric and magnetic fields • Waves can interfere • Examples – 2-slit interference – diffraction 2-slit interference diffraction ISP209s8 Lecture 14 -6- Light as a particle • Light also behaves like a particle • Light comes in small bundles of energy we call photons • Energy (of a photon) = h f h = 6.625E-34 Js = 4.136E-15 eVs armen.
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ISP209s8 Lecture 14 -10- Feynman Diagrams Feynman Diagrams are a pictorial way of writing the interaction between two particles. Example: Two electrons interacting by the Coulomb force time A line that begins and ends in a diagram corresponds to a “virtual particle”. Others are “real” particles. space ISP209s8 Lecture 14 -11- How do we know about photons? Atomic Spectra ISP209s8 Lecture 14 -12- Atoms and molecules exists fixed states of energy Ground state Excited state Transition 3.0 eV 0 eV Energy of photon = Ei – Ef = 3.0 – 0 = 3.0 eV Emission Absorption If the electron is completely removed, this is called ionization. ISP209s8 Lecture 14 -15- Bosons and Fermions • Particles come in two types • Bosons have the property that they can overlap. Examples are photons and certain atoms (helium) • Fermions can not exist in the same state. Examples – electrons, protons. • The fermion nature of elections explains atomic structure ISP209s8 Lecture 14 -16- Electron Wave functions in atoms The nucleus sits at the center and these picture show possible regions were the electrons might be. + - Old picture Examples of wave functions New Picture: ISP209s8 Lecture 14 -17- Heisenberg’s Uncertainty Principle • If a particle has a wavelength, its position and speed are not perfectly defined. • Uncertainty Principle: It is not possible to know exactly the position and momentum of a particle at the same time. • There is no absolute knowledge. The Newtonian view of the world (if everything were known, everything could be predicted) in not attainable. π4 hpx ≥ΔΔ
