Hohlraum
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In radiation thermodynamics, a Hohlraum is a cavity whose walls are in radiative equilibrium with the radiant energy within the cavity. First proposed by Gustav Kirchhoff in 1860 and used in the study
Mockup of a gold-plated Hohlraum designed for use in the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory
Black-body radiation
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Black-body radiation is the thermal electromagnetic radiation emitted from a body in thermodynamic equilibrium with its environment. A black body is an idealized opaque and non-reflective body. The ra
Hohlraum
…whose walls are in radiative equilibrium with the radiant energy within the cavity. First proposed by Gustav Kirchhoff in 1860 and used in the study of black-body radiation (Hohlraumstrahlung), this idealized cavity can be approximated in practice by a hollow container of any opaque material. The radiation escaping through…
Blacksmiths judge workpiece temperatures by the colour of the glow.
The temperature of a Pāhoehoe lava flow can be estimated by observing its color. The result agrees well with other measurements of temperatures of lava flows at about 1,000 to 1,200 °C (1,830 to 2,190 °F).
Much of a person's energy is radiated away in the form of long-wave infrared (LWIR) light. Some materials are transparent in the infrared, but opaque to visible light, as is the plastic bag in this thermal (LWIR) camera image (bottom). Other materials are transparent to visible light, but opaque or reflective in the infrared, noticeable by the darkness of the man's glasses.
Human Visible