| Modern Physics >
Quantum Effects > Photoelectric Effect |
DCS# 7A10.10 |
DISCHARGE OF
ZINC
APPARATUS
| short-wave uv lamp |
202-18-B |
| zinc plate |
202-18-B |
| electroscope |
202-18-C |
| rubber rod |
202-18-D6 |
| rabbit fur |
202-18-D5 |
| piece of glass |
101-06-E6 |
| camera |
202-09-D |
DESCRIPTION
Rub the rod with the rabbit fur to
charge it negatively. Charge the zinc plate with the
rubber rod. The electroscope can be seen to discharge when
the zinc is illuminated with uv light from the Geology mineral
lamp or a mercury spectrum tube. The electroscope does not
discharge when a glass plate is inserted to block the uv.
Alternative method: Positively charge the top plate of the
electrophorus and hold it near the uncharged zinc plate.
Use the uv light to charge the zinc.
NOTES
Rub rubber rod with rabbit fur or pvc
with paper towel to obtain negative charge on rod.
Polish the zinc with steel wool to
remove any oxide coating.
The work function of zinc is 4.33
eV, corresponding to a threshold wavelength of 287 nm.
REFERENCES
B.
Tolar, "Experiments with a photoelectric electroscope," The
Physics Teacher, vol.14, 502-503 (1976).
Freier and Anderson, Ok-3;
Meiners, 38-2.1;
Sutton, A-89.