Interactive model, with minimal support
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This activity reviews the basic characteristics of photons and light-matter interactions.
Students will be able to:
• manipulate intensity and frequency of light, including adjusting intensity and seeing its effect on the heating of matter;
• replicate in a model a beam of photons of particular intensity and frequency;
• describe three fates of light-matter interaction: passage through, absorption by and emission from matter;
• generate and read an absorption spectrum.
Additional Related Concepts
There are a few important things that we have adjusted to simulate photon-atom interactions. First, the scale of the actual wavelength for visible light is microns (10^-6 meter), much longer than we show here (angstroms, 10^-10 meter). Second, the speed of light in vacuum is about 3x108 meters per second, much faster than the photons in the model travel (~104 meters per second). We have to bring down the scale of size and speed to those of atoms, otherwise we cannot show both of them at the same time -- in reality, photons go so fast that they effectively appear to be a continuum if viewed from atoms, and atoms move so slowly that they effectively appear to be static if viewed from photons.
In addition to these adjustments, there are a few limitations of the model, listed as follows:
Light as waves. Light is not only particles but also waves (the wave-particle duality). Our model, however, cannot depict the wave behaviors of light, such as diffraction, interference, the Doppler effect and so on.
Light as rays. Our model cannot depict macroscopic optical phenonmena, such as reflection and refraction, in which light is viewed as rays of a continuum.