PURPOSE: Demonstrate the emission of photoelectrons.
DESCRIPTION: A zinc plate connected to an electroscope and charged positive will not discharge under the influence of ultraviolet radiation from the black light. When the plate is charged negative, however, UV light will discharge the plate, as indicated by the electrometer. A 1/8" glass plate inserted into the light from theUV bulb prevents passage of UV and the discharge ceases. Removing the glass plate allows the discharge to continue.
SUGGESTIONS: Zinc plate must be polished before use to clear off oxide and expose zinc surfaces.
EQUIPMENT: Black light, glass plate, zinc plate mounted on electroscope, positive and negative charging materials.
SETUP TIME: 5 min.
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