μm. Thus, a very hot star such as Sirius (11 000 K), emitting bluish-white light, radiates
with the peak of spectral radiant emittance occurring within the invisible ultraviolet
spectrum, at wavelength 0.27 μm.
10399403;a1
Figure 22.5 Wilhelm Wien (1864–1928)
The sun (approx. 6 000 K) emits yellow light, peaking at about 0.5 μm in the middle
of the visible light spectrum.
At room temperature (300 K) the peak of radiant emittance lies at 9.7 μm, in the far
infrared, while at the temperature of liquid nitrogen (77 K) the maximum of the almost
insignificant amount of radiant emittance occurs at 38 μm, in the extreme infrared
wavelengths.
140 Publ. No. T559382 Rev. a358 – ENGLISH (EN) – June 23, 2009
22 – Theory of thermography
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