PASCO TD-8555 THERMAL RADIATION SYSTEM - Manual (Page 25)

012-04695D Thermal Radiation System
21
② The lamp filament is not a true black body. If it
were, it would be completely and totally black at
room temperature. It is a fairly good approximation,
though, as long as the temperature is high enough
that the emitted light is much greater than the inci-
dent light.
③ Any other thermal source in the room would influ-
ence the results, including the warm body of the ex-
perimenter and the room itself. These introduce
some error, but it is small as long as the tempera-
ture of the lamp is high compared to the tempera-
ture of these other sources.
Experiment 4: Stefan-Boltzmann Law (at low temperatures)
Notes on Procedure
③ Make sure that the Thermal Radiation Cube has
been off for enough time to be at equilibrium with
the room before making this measurement. If the
cube has been turned on recently, use another ther-
mometer to make the measurement.
⑤ Use ridiculous precautions with this experiment. It
is impossible to have too much insulation between
the cube and the sensor between measurements. For
our experiments, we use two foam sheets covered
with aluminum tape, and an air gap between the
sheets. We never removed this heat shield for more
than 5 seconds while taking a measurement.
Calculations
1
1
1
1
1
1
1
0
2
4
6
8
10
12
14
16
18
0
2000000000 4000000000 6000000000 8000000000
10000000000 12000000000 14000000000
Radiation (mV)
Difference in T^4
f(x) = 1.235365E-9*x + -1.396775E-1
R^2 = 9.881626E-1
Notes on Questions
① The linearity of this graph indicates that the Stefan-
Boltzmann equation is correct, even at low tempera-
tures.
② The graph should be straight, with some statistical
variations.