CHED 408 |
| In general chemistry, the interaction of light and matter arises early in the discussion of spectroscopy. In order to explain this interaction, most texts rely on the photon aspect of light, which accounts for energy balance through the Bohr-Einstein relationship, hν = Ef - Ei , but does not describe the mechanism of energy exchange. In our approach, we focus on the wave aspect of light to introduce the key mechanistic idea that in the absorption and emission of light, the oscillating electric field of the light causes the electron charge cloud of an atom or molecule to oscillate synchronously, much like Jell-O® jiggles when shaken at one of its natural frequencies. The "natural frequencies" of the electron charge cloud are given by νcloud = (Ef - Ei)/h; we emphasize that the Bohr-Einstein relationship really describes frequency matching νlight = νcloud = (Ef - Ei)/h. We offer these insights to students through bridging analogies from mechanical and acoustical systems, and then introduce them to the quantum role of time: (1) if matter has a well defined energy, it does not change with time, but (2) whenever there is any mixing of energies, there are corresponding oscillations. Our pedagogical method relies on software to guide students through a visual investigation of the Bohr-Einstein relationship (http://quantumconcepts.bu.edu). |
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Teaching Quantum Concepts in Chemistry
1:30 PM-4:45 PM, Tuesday, 12 September 2006 San Francisco Marriott -- Salon 6, Oral
Division of Chemical Education |