7A10.10 - Photoelectric Effect in Zinc
Video Credit: Jonathan M. Sullvan-Wood.
Polish the zinc plate with the steel wool immediately before doing the demo. Charge the electroscope with the negative rod. Note that you can discharge the electroscope only with the short wavelength UV light or the arc lamp. Next charge the electroscope with the positive rod. Note that the UV lights can not discharge the electroscope as there is no excess of electrons to drive off.
This experiment can also be done with aluminum instead of the zinc as aluminum has an almost identical work function. A simple aluminum plate that works well can be made by sanding the paint off an aluminum pop can and attaching it to your electroscope. Then just use it as you would the zinc plate. You will have to also rub the aluminum with steel wool before each use to strip off the aluminum oxide coating that develops rather quickly.
NOTE: It is easier to sand the paint off the pop can if the pop can is unopened. Once you have an appreciable area sanded exposing the aluminum metal, you can open the can, drink the contents, and THEN perform the demonstration.
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