The author has a radiometer that is about 80 years old that he uses in demonstrations for various audiences. When exposed to light, the “fan” turns very fast, then slows down, and eventually comes to rest. But when I touch the glass with my hand, the whirling starts again. Sometimes, before restarting, the fan turns in the opposite direction for awhile. Why?
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© 2002 American Association of Physics Teachers.
2002
American Association of Physics Teachers
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