3B Scientific Determination of Planck's Constant (h) Apparatus User Manual
Page 2
Elwe Didactic GmbH • Steinfelsstr. 6 • 08248 Klingenthal • Germany •
www.elwedidactic.com
3B Scientific GmbH • Rudorffweg 8 • 21031 Hamburg • Germany •
www.3bscientific.com
Subject to technical amendments.
3. Technical data
Operating voltage:
6 V DC
Maximum permissible
current:
20 mA, LED (infra-red)
100 mA
Diodes:
6 LEDs (blue, green, yellow,
and 3 different wavelengths
of red)
Series resistor:
100 Ohm, 1 W
Connections:
4-mm safety connectors
Dimensions:
115 mm x 115 mm
Weight:
120 g approx.
4. Sample experiments
In order to conduct the experiments, the following
apparatus is additionally required:
1 DC power supply unit,
0-30 V, stabilised:
8521145
1 Multimeter, Escola 10
8531160
1 Stand base
8611210
Experiment leads
4.1 Determining Planck’s constant (h)
•
Connect the diodes individually via the resistance
to the voltage source. Make sure they are forward
biased.
•
Switch on the power supply unit after setting it to
the minimum voltage.
•
Gradually increase the voltage.
The diodes light up when the bias voltage U
D
(between
connections 1 and 4) has been reached.
For a wavelength of 950 nm, the light emission can be
observed through the viewfinder of a digital camera.
4.2 Evaluation
•
Calculate the frequency values from the wave-
lengths.
f = c/
λ
•
Calculate the values for energy.
E = e *10
-19
·U
D ,
•
Based on the energy values in the E/f curve, calcu-
late the gradient of the curve.
•
Derive the constant (Planck’s constant h) from
the gradient.
f
h
U
e
D
⋅
=
⋅
λ (nm)
Colour
f in 10
14
Hz
f = c/
λ
U
D
in V
Measurements
E = e * U
D
in J*10
-19
(e = 1.602*10
-19
As)
465
Blue
6.45
2.26
3.62
560
Green
5.36
1.72
2.76
585
Yellow
5.12
1.67
2.67
635
Light red
4.72
1.51
2.419
660
Dark red
4.54
1.44
2.307
950
Infra-red
3.15
1.0
1.6