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Photoelectric Effect in Zinc
Purpose:To show that UV light of sufficient energy incident on a Zinc plate can cause electrons to be emitted from the metal's surface.
Procedure:Attach the Zinc plate to the top of the electrometer and charge with the teflon rod and silk so that there is a noticable displacement of the electroscope leaves. Place the UV light next to the Zinc plate and turn it on. The loss of charge due to photoelectric emission can be seen by watching the electroscope leaves fall back to a vertical position. (note: the UV light has short-wave (sw = 254nm) and long-wave (lw = 366nm) settings. Only at the sw setting electrons will be emitted from the Zinc plate).
Hints:The work function for zinc is approx. 4.31 eV which gives a cutoff wavelength of 288 nm.
Zinc surface should be cleaned with steel wool before use.
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