Teacher’s guide, Experiment 1: introduction to thermal radiation, Experiment 2: inverse square law – PASCO TD-8555 THERMAL RADIATION SYSTEM User Manual
Page 23: Calculations
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Thermal Radiation System
19
Calculations
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1
1
1
1
1
1
1
1
1
11
1
1
1 1 1
1
1
1
1
1
1
1
0
5
10
15
20
25
30
0
10
20
30
40
50
60
Radiation (mV)
Distance (cm)
f(x) = 2.060229E+2 * (x^-1.815646E+0 )
R^2 = 9.822989E-1
③
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
5
10
15
20
25
30
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
Radiation (mV)
1/x^2
Teacher’s Guide
Experiment 1: Introduction to Thermal Radiation
Notes on Questions
Part 1
① In order of decreasing emissivity, the surfaces are
Black, White, Dull Aluminum, and Polished Alumi-
num. This order is independent of temperature; and
within the temperature range tested, the ratio of
emissions between sides is almost constant. The
normalized percentages are as follows: (Black is
defined as 100%)
Surface
Normalized
Emissions
Standard
Error
Black
100
White
96.86
±1.21%
Dull
20.23
±2.17%
Polished
7.38
±1.82%
② Measurements are consistent with the rule. The bet-
ter reflectors (poorer absorbers) are poor emitters.
Notes on Questions
Part 2
① Yes. All sides of the Leslie’s Cube are at the same
temperature, but the polished side emits less than
10% as much radiation as the black side.
② Materials that block thermal radiation well include
aluminum foil, styrofoam, etc. Materials that do not
block radiation as well include air, clothing, etc. All
materials will block radiation to some degree, but
there are strong differences in how much is
blocked.
Notes on Questions
Absorbtion and Transmission of Thermal Radiation
① Heat loss through (closed) windows is primarily
conductive. Although the glass tested transmitted
some infrared, most was blocked.
② A greenhouse allows light in, but does not allow
much heat to escape. This phenomenon is used to
grow tropical plants in cold climates.
Experiment 2: Inverse Square Law