Photo by V. Miller
Sept. 13, 2006
Zinc and the Photoelectric Effect
Will the Thermal Expansion of a Zinc Plate Undergoing the Photoelectric Effect Cause More Photoelectrons to Be Emitted?
Alexander Uribe, 14, Eagle Mountain, Utah
National Park Service Explorer Team Award, Discovery Channel Young Scientist Challenge, 2005
Project background: Alexander became fascinated with quantum physics in general and the photoelectric effect in particular. He enjoyed experimenting and wanted to learn more.
Tactics and results: Alexander built an apparatus that heated a zinc plate. He mounted it on an electroscope, which measured the number of photoelectrons that the plate emitted. He charged the zinc plate by rubbing a polyvinyl chloride (PVC) pipe with silk and rubbing the charged pipe against the plate. He heated the plate to different temperatures and recorded how long it took the electroscope to reach a reading of zero—that is, for the plate to release all its charge. He hypothesized that as the plate got hot and expanded, it would discharge more photoelectrons than it did when it was cold.
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| Photo by V. Miller |
Alexander confirmed his hypothesis: A heated plate discharged photoelectrons much faster than a cool plate did.
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