Chapter

Modern Introductory Physics

pp 553-567

Date:

The Heisenberg Uncertainty Principle

  • Charles H. HolbrowAffiliated withCharles A. Dana Professor of Physics, Emeritus Email author 
  • , James N. LloydAffiliated withDepartment of Physics & Astronomy, Colgate University
  • , Joseph C. AmatoAffiliated withWilliam R. Kenan, Jr. Professor of Physics, Emeritus Department of Physics & Astronomy, Colgate University
  • , Enrique GalvezAffiliated withDepartment of Physics & Astronomy, Colgate University
  • , M. Elizabeth ParksAffiliated withDepartment of Physics & Astronomy, Colgate University

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Abstract

The photoelectric effect showed that waves behave like particles. A wave with a frequency f has a minimum packet, or quantum, of energy E = hf, where h is Planck’s constant. Compton showed that when hf is comparable to the rest mass energy mc 2 of an electron, the scattering of electromagnetic radiation from electrons behaves like the scattering of one compact object from another. The particle-like behavior of light seems so prominent in these cases that the quantum of light has been given the particle-like name of “photon.” Individual photons can be detected with a photomultiplier tube; such detection also suggests a degree of localization in space that is characteristic of particles rather than waves.