HONR228Q Notes section d:

  • Quantum Mechanics

    1. What is involved?

      1. Deals with objects that are "submicroscopic"
        1. Photons
        2. Electrons
        3. Protons and neutrons
        4. Atoms
        5. Nuclei
        6. Sub-nuclear particles
      2. Requires new "laws" of physics
        1. Schroedinger equation supercedes Newtons laws of motion
        2. Standard mechanics becomes "wave mechanics"
        3. Leads to "quantization:" indivisible units of mass, charge, etc.

    2. "Waves" as "Particles"

      1. Photoelectric Effect Experiments
        1. DEMO P2-02: PHOTOELECTRIC EFFECT IN ZINC - ARC LAMP
        2. DEMO P2-01: PHOTOELECTRIC EFFECT AND PLANCKS CONSTANT
      2. Interpretation of experiments
        1. Single photon ejects single electron from metal surface
        2. Photon energy E proportional to frequency f: E=hf, c=fl
          3. where c is the speed of light and l is the wavelength
        3. Constant of proportionality for photon energy is h = Planck's constant
      3. Applications of the photoelectric effect
        1. DEMO P2-06: PHOTOELECTRIC TRUCK
        2. DEMO P2-05: PHOTO-RESISTOR RELAY
        3. Solar cells convert light into electric current
      4. Meaning of EM waves as "ionizing radiation"
        1. Refer to slide: f, l, and E for various electromagnetic waves
        2. Electron-volt (eV) as unit of energy E
        3. Power line photons low frequency, no ionization, no danger
        4. IR photons ~ fraction of eV (can raise molecular state)
        5. Light photons ~ few eV (can raise atomic electron levels or ionize atom)
        6. UV photons ~ 10 eV (are dangerous to your skin, but do not penetrate)
        7. X-ray photons ~ 1 keV (readily penetrate and damage tissue)
        8. Gamma-rays ~ 1 MeV (very dangerous in large quantities)

    3. "Particles" as "Waves"

      1. "de Broglie wave" Experiments
        1. DEMO P2-14: ELECTRON DIFFRACTION MODEL
        2. DEMO P2-13: ELECTRON DIFFRACTION
      2. Interpretation of results
        1. Wavelength l=h/p, where p is the particle momentum
        2. Electron diffraction as example of wave behavior of particles
        3. Electrons diffract to form patterns as light waves do
      3. Application to how we "see" very small objects
        1. FILM LOOP: DIFFRACTION AND SCATTERING AROUND OBSTACLES
        2. Must use "light" with wavelength less than the size of the object we are viewing
        3. Limit is when the "light" diffracts around object being observed
        4. Greater mass particles have shorter wavelength and see in greater detail
        5. Greater momentum (greater kinetic energy) have shorter wavelength
        6. For "large" objects we use light
        7. For atoms or crystal structures we must use x-rays or electrons
        8. For nuclei we must use very energetic electrons or protons (with very short wavelength)

    4. The two-slit interference paradox

      1. Background materials
        1. DEMO M1-13: INTERFERENCE - KLINGER TRANSPARENT SLIDES
        2. DEMO H2-21: AUDIBLE YOUNG’S EXPERIMENT - GROUP LISTENING
        3. FILM LOOP: INTERFERENCE OF WAVES
        4. DEMO M1-01: LASER DIFFRACTION - FIXED SINGLE SLITS
        5. DEMO M1-11: LASER DIFFRACTION - FIXED DOUBLE SLITS
      2. Experiment
        1. DEMO P2-11: INTERFERENCE OF PHOTONS
      3. Interpretation of results
        1. One of the great paradoxes of physics
        2. Two-slit interference pattern from statistics of individual photons
        3. Demonstrates that a photon interferes with itself
        4. Each photon must pass through both slits

    5. Quantum nature of atoms and nuclei

      1. Elementary particles
        1. Masses and charges are quantized
        2. DEMO K1-12: CATHODE-RAY TUBE - DEFLECTION BY MAGNET
        3. DEMO P3-21: CATHODE-RAY TUBE - SHADOW EFFECT - MALTESE CROSS
      2. Atoms and nuclei
        1. Energy levels are quantized
        2. Transitions between levels are quantized
      3. Experimental basis
        1. DEMO P2-31: E/M OF ELECTRON APPARATUS
        2. Helps to show that the charge and mass of the electron are quantized

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