FLIR Ranger HRC MS - Page 249

Ranger HRC™ operator´s manual – Theory of thermal imaging
Publ. No. TM G007971 Rev. A1 – ENGLISH (EN) – Sept 09. 2008 239
Planck’s formula, when plotted graphically for various temperatures,
produces a family of curves. Following any particular Planck curve, the
spectral exitance is zero at l = 0, then increases rapidly to a maximum at
a wavelength l
max
and after passing, it approaches zero again at very long
wavelengths. The higher the temperature, the shorter the wavelength at
which maximum occurs.
1
2
900 K
800 K
700 K
600 K
500 K
8
7
6
5
4
3
2
1
1 3 5 7 9 11 13 15
Figure 17.4 Blackbody spectral radiant exitance according to Planck’s law, plotted for
various absolute temperatures. 1: Spectral radiant exitance; 2: Wavelength (μm).