what causes a resistor to turn current into radiation?

[paulca]

Yes.  But for those you need radioactive elements.

[TimFox]

Oops--I misread the context of your statement about requiring fission.

[T3sl4co1l]

Technically no, thermal is x-rays -- even at 1MeV+.  X-rays are produced by electron interaction, gamma by nuclear reaction.

So the ~10keV emission from tritium is gamma, even though it's eminently within the realm of electrically produced x-rays.

Well, I suppose it might be worth arguing that x-rays from a hot proton, neutron, and other nucleons, plasma (or all the way up to quark-gluon plasma even) might be gammas, but anyway, such cases are clearly where the distinction lacks value.


As for black body, it may get complicated at extreme temperatures, where pair production (>1MeV) enables additional degrees of freedom.  You still have the same old Planck distribution among photons -- there are just have additional forms of radiation as well.

I think the consequence of this is, not so much the spectrum changing, as the heat capacity of space itself going up -- in addition to EM modes, electron and etc. modes become available.  Again using the equipartition theorem, when all these modes are in thermal equilibrium, each has a distribution given by its statistics (an electron-positron gas will have a Maxwell-Boltzmann distribution, I think?).

Tim

[TimFox]

Because of the definition (by source, not energy), there is a large overlap between x-ray energies and gamma energies.

[paulca]

Because of the definition (by source, not energy), there is a large overlap between x-ray energies and gamma energies.

Yeah.  Sounds like two slightly out of sync models interacting.  Not uncommon I suppose.  As long as the electro-magnetic effects remain the same I suppose and ... gammas are electromagnetic.

[TimFox]

No, just a question of definition.  The other common forms of radiation are defined (roughly) by wavelength (some overlap between short microwave RF and long infrared wavelengths) but X rays and gammas were named before it was determined that they were EM radiation as well.  We now understand that they are all of the same nature.   Luckily, we no longer need to consider “N rays” (q.v.).

[Berni]

Yeah the exact borders of what we call different wavelengths of electromagnetic radiation are pretty fuzzy since the effects they are usualy named after morph into one another gradually rather than at one single sharp wavelength.

You could just as easily split up X-rays into various bands of higher or lower energy ones, Like for example we have UV-A, UV-B and UV-C, tho with that we had a good reason to give it separate names since it has different effects. UV-A is considered fairly safe, higher energy UV-B not anymore since it gives you burns, even higher energy UV-C instead is so energetic that it rips oxygen apart just by shining trough air. But once you go even higher and get to x-rays they get powerful enough to rip apart just about anything. But they still have similarity as in high energy UV-C has a lot of the chemical bond wrecking ability of X-Rays, while low energy X-Rays have the property of easily being stopped by almost anything (like UV light).

For example Extreme UV (EUV) straddles this line as its actually considered low energy X-rays rather than UV and the latest and greatest chip making lithography process uses 13nm (or about 100eV) EUV light to get around the wavelength limitations. Tho making such EUV light and focusing it gets really really tricky.

[TimFox]

Again, definitions.  Usually, people say “light” if you can focus it.  However, radio waves can be focused with antenna structures (Hertz made lenses out of pitch) and X-ray focusing mirrors have been made using glancing incidence.  The distinction is more engineering than physics.

[iteratee]

Many of my teachers at one point referred to the "visible" spectrum as "narrow". They've all been looking at the same logrithmic chart zeroed at D.C.

[TimFox]

The visible spectrum is less than one octave wide.  The radio classifications (mf, hf, vhf, uhf, etc.) are each a full decade wide.  This is a normal way to express spectrum width.  Full audio bandwidth (20 Hz to 20kHz) is 10 octaves.

[cdev]

Heat motion of electrons is a given at any temperature above absolute zero? Is that right?

[TimFox]

At absolute zero, due to quantum mechanics, there is still zero-point energy.  This is a complicated subject:  I refer you to the textbooks.  Since electrons have spin-1/2, they obey Fermi statistics, another complicated subject.

[T3sl4co1l]

There can be motion (for whatever counts as motion in the quantum world) at zero temperature, just not non-degenerate state transitions, because there's no energy to move between states.

Tim