Summer School 2010.5: Quantum Physics

The midpoint in our series on Quantum Mechanics is available here.

4 replies on “Summer School 2010.5: Quantum Physics”

  1. Here are my thoughts and comments:

    1) I remember hearing that the “solar system” model of the atom is misleading and incorrect, that the electrons don’t actually orbit the nucleus in the same way that planets orbit the Sun. Instead, they sort of hover at a distance from the nucleus (with the ability to move around and in/out, of course). Is this correct, and if so, should you be perpetuating a misleading model of the atom?

    2) Regarding sections 3.2 through 3.4. So as I understand it, the speed and wavelength of light will change as it goes from, say, air to water, but they will change in such a way that the frequency remains constant. Is that correct?

    3) On a side not, I find it interesting that there is a maximum intensity for sound waves through air, because it gets to the point where the wave trough is vacuum.

    4) In section 6, regarding this sentence: “Doubling the frequency of light would double the stopping voltage.” The definition of “stopping voltage” come after this sentence (in problem #1). And even within problem #1, the parenthetical definition appears during the second mention of the voltage required to stop the current.

    5) In section 7, regarding this phrase: “Planck’s math had already indicated that this energy would be directly related to the frequency. He refused to believe the quantized light interpretation because of the Poisson spot, but he published anyway because the math worked so well.” Is the “He” in the second sentence Einstein or Planck?

    6) It would probably help if, somewhere early in section 7, you specifically stated that, in the particle view, intensity is related to the number of particles.

    • 1) That’s the picture we started with here because it’s the one most readers will be starting with. It will be thoroughly dismantled shortly. (Lesson 7, part 6, actually.)

      2) Yes, that’s correct. Speed is the product of wavelength and frequency, so if wavelength drops by 10%, speed also drops by 10%, so that the frequency remains constant.

      4) I’ll go through and edit.

      5) Plank.

      6) Noted.

    • 3) Good point; that would be an interesting shape for a sound wave. (Although just because the wave trough is a vacuum doesn’t mean the peaks can’t compress anymore, so I suspect the sound wave intensity has a maximum even then.)

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