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For more information, please see full course syllabus of AP Physics B
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Lecture Comments (2)

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Post by Jamal Tischler on May 31, 2015

Great explainations and proof ! That statement Bohr made(mvr=nh/2pi) , comes from (matter waves lesson), the wavelenght associated to the electron. We can say of the lenght of the orbit: L=2*pi*r=n*lambda. Where lambda is the wavelenght associated to the electron. This is a standing(or stationary) wave on a circular path. And the condition n*lambda comes from the maximum in any wave interference. But lambda=h/mv. I hope you will find this explaination helpful.

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Post by Jay Gill on June 3, 2013

Very knowledgable but lectures are too long- too much time is taken to elucidate point. For example, slow speech, and lots of miniature pauses between conveying thoughts. I apologize for the honesty but students are sometimes pressed for time.

Hydrogen Atom

  • In 1911, Rutherford established that an atom has a positively charged nucleus, which contains most of the mass of the atom. Surrounding the nucleus are light, negatively charged electrons.
  • It was observed that the emission spectra of hydrogen atoms consisted of some sharp lines with well defined wavelengths.
  • Bohr model: In 1913 Bohr presented a model of the hydrogen atom, in which the electron was assumed to move in a circle about the nucleus. Bohr assumed that only certain orbits were allowed, and that the atom emits or absorbs a photon when the electron makes a transition from one orbit to another. He succeeded in deriving the line spectrum of hydrogen. However, almost nothing else could be explained by this model, and there was no way to extend it to other atoms.
  • It took the emergence of quantum mechanics, as developed by Schrodinger, Heisenberg, and others, to set the stage for the new era of modern physics.

Hydrogen Atom

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Nuclear Model 0:12
    • J.J. Thomson Discovered Electrons
    • Rutherford Experiment
    • Example: Solar System
    • Planetary Model
    • Centripetal Acceleration
  • Line Spectra 18:48
    • Low Pressure Gas Connecting to High Voltage
    • Group of Wavelength
    • Emission Spectra
    • Lyman
    • Balmer Series
    • Pascen Series
  • Bohr's Model 27:14
    • Electron in Circular Orbit
    • Stationary Orbits
    • Radiation is Emitted When Electron Makes Transition
    • For Each Orbit Mass, Speed, Radius
  • Quantized Energy of the Bohr Model 35:58
    • Electron in Circular Orbit
    • Total Energy
  • Line Spectra Intercepted 46:12
    • Energy of Orbit
    • Balmer Series
    • Paschen Series
  • Example 54:57
    • N=1 and N=2
  • Extra Example 1: Balmer Series for Hydrogen
  • Extra Example 2: Minimum n for Hydrogen
  • Extra Example 3: Energy to Transition Electron