Recently I found myself becoming confused over a topic that I thought I had previously understood.

In a theoretical blackbody which reaches thermal equilibrium the energy absorbed is equal to the energy emitted by the body. So if that equilibrium becomes disturbed and over some time period there is more energy being absorbed than emitted, the body's temperature will rise until it is emitting enough energy to balance the incoming energy. This much seems clear.

What if we were to continuously supply a blackbody with incident radiation and it was highly insulated so that barely any energy could be emitted and the temperature kept rising? If this temperature continues to rise can the body become hot enough to emit electromagnetic waves that are of a shorter wavelength than any of the incident radiation that it absorbs? If an object keeps heating due to an energy supply I don't see why it couldn't, but I have read several places (perhaps incorrectly or misunderstanding) that an object cannot emit electromagnetic waves of a higher energy than it receives. Shouldn't it just get hotter and begin to partition its energy among the different wavelengths of light at different intensities and that combination is characteristic of a given temperature of the object in question?

What led scientists in the early 20th century to the absurd result of the UV catastrophe? I know it has something to do with them falsely believing that the hotter an object became the more it would disproportionately emit shorter wavelengths resulting in infinite power. What is a conceptual reasoning for this?

  • $\begingroup$ I think this link is clear enough. hyperphysics.phy-astr.gsu.edu/hbase/mod6.html $\endgroup$ – anna v Jun 3 '19 at 4:34
  • $\begingroup$ Reading this, it seems to imply to me that a body can emit wavelengths which are shorter than the ones it absorbs, though none of that is really explicitly stated here. It's pretty insightfull on the whole blackbody problem though, regardless. $\endgroup$ – MattGeo Jun 3 '19 at 21:59
  • $\begingroup$ Yes it can, because it might absorb the energy of a laser pulse , a specific frequency, but it will emit a broad spectrum as black body radiation at the temperature it reaches, which is obvious from the spectrum of black body . This is because the statistical distribution of kinetic energies of the molecules involved in black body radiation is a broad spectrum. $\endgroup$ – anna v Jun 4 '19 at 2:53

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