®
Model No. AP-8209
Photoelectric Effect Apparatus
26
Student answers will vary. One possible reason for the difference is this: Because the photocurrent
is so small, it is somewhat difficult to set the VOLTAGE ADJUST knob to the precise value of
stopping potential that will cause the photocurrent to be zero. In addition, nearby electronic devices
such as computer monitors may influence the sensitive meters in the apparatus.
3.
How can you find the Work Function from the graph of Stopping Potential versus
Frequency?
The work function divided by the charge of the electron,
e
, is the y-intercept on the graph. Multiply
the value of the y-intercept by
e
to find the value of the work function,
W
0
.
Extension Questions:
1.
How does your calculated value of
h
for each different aperture compare to the accepted
value,
h
0
, 6.626 x 10
-34
J s?
Answers will vary.
2.
How does light intensity affect the Stopping Potential?
Light intensity does not appreciably affect the Stopping Potential?
Questions: Experiment 2 - Constant Frequency
1.
How do the curves of current versus voltage for the one spectral line at three different
intensities compare? In other words, how are the curves similar to each other?
The current versus voltage curves for one spectral line and three different intensities are similar in
that the stopping potential, -1.1 V, is the same for all three curves. The curves have the same overall
shape.
2.
How do the curves of current versus voltage for the one spectral line at three different
intensities contrast? In other words, how do the curves differ from each other.
The current versus voltage curves for one spectral line and three different intensities are different in
the following way: The amount of photocurrent increases as the size of the apertures increase.
Increased intensity increases the amount of photocurrent.
Questions: Experiment 3 - Constant Intensity
1.
How do the curves of current versus voltage for the three spectral lines at a constant intensity
compare? In other words, how are the curves similar to each other?
The current versus voltage curves have similar overall shapes.
2.
How do the curves of current versus voltage for the three spectral lines at a constant
intensity contrast? In other words, how do the curves differ from each other.
The current versus voltage curves differ in that each curve has a different stopping potential. The
stopping potentials increase as the frequency increases (or wavelength decreases).
