23 3 Quantum Mechanics
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23 3 Quantum Mechanics



Light: Wave or Particle?

Light: Wave or Particle?



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23 3 Quantum Mechanics 23 3 Quantum Mechanics Presentation Transcript

  • 23-3 Quantum Mechanics
    • The Dual Nature of Light
    • A. Light is both a wave and a particle.
    • 1. The photoelectric effect is an
    • example of light behaving as a
    • particle (photon).
    • 2. Diffraction and interference are
    • examples of light acting as a wave.
    • A single photon’s energy is too
    • small to detect but a “trillion”
    • photons together behave as a
    • wave.
  • II. Matter Waves
    • Louis De Broglie theorized that all matter exhibits wave properties! We don’t notice because the effect is so small on objects larger than subatomic particles.
    •  =h/p; p=mxv
    • F=E/h
    View slide
  • B. Davisson and Germer discovered that electrons could be diffracted. (fig. 23-18)
    • Supported wave theory that particles have
    • wave properties.
    View slide
    • DeBroglie waves account for the allowed orbits of Bohr’s model .
    • There is always an integral number of electron wavelengths around each circumferrence.
    • Explains why only certain orbits are allowed. (fig. 23-19).
  • III. The Heisenberg Uncertainty Principle
    • It is not possible to know the location and momentum of a particle at the same time. This is because electrons and photons are so small, just shining light on them makes them move. (fig. 23-20)
  • IV. The Electron Cloud
    • In 1926 Erwin Schrodinger proposed a wave equation that described the way matter waves change in space and time.
    • An electron’s position is described by the Probability of finding it in a certain location!
    • Quantum mechanics also predicts that the wave function for the hydrogen atom in the ground state is symmetrical.
    • This is called the electron cloud.
  • In Closing: The quantum model of the atom is more difficult to visualize than the Bohr model, but it is also more complete.
  • In Closing (Continued) While most scientists believe that quantum mechanics may be the final picture of the deepest levels of nature, a few continue to search for other explanations.