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is made in parallel to the photocell in this case, the
voltage at the amplifier input decreases as the light
intensity is increased.
R2 and C1 provide smoothing of the collector
voltage, and R2 also protects the photocell tube.
3. Operation
•
Take the photocell tube out of the packaging
and carefully plug it into the base.
•
Protect the photocell from direct sunlight!
4. Sample experiments
4.1 Demonstration of the photoelectric effect
For carrying out the experiment, the following
additional equipment is needed:
1 DC power supply, 500 V (230 V, 50/60 Hz)
or
1 DC power supply, 500 V (115 V, 50/60 Hz)
1 Digital multimeter
Light source
Stand and clamps or optical bench
Type:
Cathode:
Effective cathode area:
Wavelength for max. sensitivity:
Anode/cathode capacitance C
Collector voltage U
:
b
Working resistance R
:
a
Dark current I
:
o
Sensitivity:
Max. photoelectric current
density I
:
k
Max. ambient temperature:
U33000-230
U33000-115
U118091
5 Technical data
U8482415
Valvo 90CV
Caesium on oxidised silver
2.4 cm²
850 nm
:
0.6 pF
AC
50 V, max. 100 V
1 MΩ
0.05 µA
20 µA/lumen
3 µA/cm²
50° C
The
experiment
dependence of the photoelectric current on the
light intensity.
•
Set up the photocell using a stand and clamps
or an optical bench (Fig. 2).
•
With a constant collector voltage U
completely darkened room, place a light
source (an optical lamp or a low-power light
bulb) at a measured distance from the
photocell.
•
Read the value of the photoelectric current on
the multimeter.
•
Move the light source so that the distance to
the photocell is half the previous value and
again read the photoelectric current.
Halving the distance has the effect of quadrupling
the photoelectric current.
2
demonstrates
the
b
U8482445
Valvo 90CG
Caesium on oxidised silver
2.4 cm²
850 nm
0.6 pF
50 V, max. 90 V
1 MΩ
0.1 µA
125 µA/lumen
0.7 µA/cm²
50° C
linear
and in a
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