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Photoelectric Effect Discovery

July 2nd Fact-of-the-Day

Heinrich Herz was a Professor of Physics at Karlsruhe and Bonn. In 1887 one his students, Wilhelm Hallwachs, made a very important and unanticipated discovery while experimenting with electric sparks. Herz and his students were trying to measure the length of sparks produced by an induction coil and they decided to darken the room to make the sparks easier to see. They expected the sparks would appear to be longer in the darkened room, because it would be possible to see dimmer portions at the ends, but Wilhelm Hallwachs noticed they were dramatically shorter. In making that observation he had accidentally discovered the photoelectric effect which later provided the basis for development of photo cells, TV camera imaging devices, and various other light-sensitive electronic devices. ©2005 Martek, International. All rights reserved.


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