At this point I still need to provide more background information on energy which they may not have had yet. So I talk about work and kinetic energy. The eV is a unit of energy which they probably have not encountered before so I need to go into converting between eV and Joules. I also want them to understand how much energy an electron has that is accelerated by a given voltage. For example an electron accelerated by 100 V has 100 eV of energy. They always get confused by this especially when you go to kV and keV. They want an equation so I guess the equation is E=qV with q in electron charge, V in volts and E in eV. Next I can go on to the energy of the photon, E=hf.

The main quantum mechanics concepts I want to cover are: Photoelectric effect, wave particle duality, characteristic energy, quantum numbers, electron spin, electron tunneling and quantum entanglment.

The photoelectric effect is good because they now have enough tools to do some real calculations. Given a certain metal with a work function and a photon of a certain wavelength what is the velocity of the emitted electron? This is nice because it has many interesting applications such as photovoltaic devices. The Hyperphysics web site has a good description of this:


This lays the ground work for discussing the operation of the electron microscope in the next unit.

Next I do a discussion of the double split experiment and how it compares between bullets, waves and electrons. I have the students work through the following web site for this:


I based my lecture off of Feynman's Six Easy Pieces, Chapter 6


Here are some images of a double slit experiment both when it is not observed and when it is observed:

I can introduce the de Broglie relation now and have them work out the wavelength of an electron. This will set an ultimate limit to the resolution of the electron microscope.

That's as far as I got this week. The next section will be on characteristic energy and spectroscopy.

For this section I do a wave lab using slinkys. Some of you probably have better slinky labs than this so I would appreciate suggestions. I want them to get an idea of how waves interfere and pass through each other, standing waves, nodes, discrete energy levels of the slinky, so that when we go on to spectroscopy I can refer back to something they know. Another good thing was we could do the slinky lab outside.

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Comment by TINC on September 20, 2008 at 11:38pm
One post was deleted by the TINC staff! Please dont add comments with more e-mail addresses, telephon nr.-s!

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Comment by TINC on September 19, 2008 at 11:18pm
thanks Hans

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