FLIR ThermaCAM PM575 Operator's Manual page 61

2πhc
Wλ = ---------------------------------------
b hc λ kT ⁄
5
λ (
e
where:
W λ = the blackbody spectral radiant emittance at wavelength λ.
b
c = the velocity of light = 3 x 10
h = Planck's constant = 6.6 x 10
k = Boltzmann's constant = 1.4 x 10
T = the absolute temperature (K) of a blackbody.
λ
= wavelength (m).
N.B. – The factor 10
2
in Watt/m µm. If the factor is excluded, the dimension will be Watt/m
Planck's formula, when plotted graphically for various temperatures, produces a
family of curves. Following any particular Planck curve, the spectral emittance is
zero at λ = 0, then increases rapidly to a maximum at a wavelength λ
passing it approaches zero again at very long wavelengths. The higher the temper-
ature, the shorter the wavelength at which maximum occurs.
Figure 9.2 Blackbody spectral radiant emittance according to Planck's law,
plotted for various absolute temperatures.
© FLIR Systems AB – Publ. No. 557 369 – Ed. A
2
6 –
× [
10 Watt m
)
– 1
-6
is used since spectral emittance in the curves is expressed
2
⁄ µm ]
8
m/sec.
-34
Joule sec.
-23
Joule/K.
[9.3.1 — Planck's law]
2
m.
and after
max
53