7A10.10 - Photoelectric Effect
This demonstration shows the production of photoelectrons in zinc.
Clean one face of the zinc plate with steel wool immediately before doing the experiment or the effect will not be seen. The plate is then suspended from a Plexiglas rod with string and a banana lead is alligator clipped on from it to a projection electrometer. A UV light source with no lens is set up fairly close to the plate to illuminate the side which was cleaned.
Be sure to align the UV light so that none of the light shines above or below the plate as it is usually set up where the light is facing the students. Danger signs are important here.
Using the piezoelectric charger, squeeze the charger and touch the ground plate. Then, while still having the charger squeezed, release the squeeze with the charger contacting the zinc plate. This will deposit positive charge onto the zinc plate. Then turn on the UV light and remove the clear plastic plate out of the way. You should see the charge on the electroscope drop down due to the photoelectric effect. You can prove this is what is happening by then repeating the experiment with negative charge instead of positive charge.