A lightbulb is painted black..

[Kalmah]

This might not be 'highly technical' but I'm still curious.

No light can escape from the bulb, but it continuously creates light.. In theory, wouldn't it 'fill up' and then eventually explode? (I don' believe this would happen.. it just seems like a logical theory) ... rhetorical

Does the light just dissipate into heat?

 

[slpaulson]

I think your black paint would absorb the visible light, and radiate energy out at a different frequency.

It would get hot too.

I think the scenerio you are describing is if the lightbulb was a perfect mirror on the inside.

 

[silverpig]

The light will hit the inside of the bulb and be absorbed. The light bulb will then heat up and radiate the heat away. If the source inside the bulb is powerful enough, the outside will then glow depending on its temperature.

 

[Paratus]

It's a simple black body radiator at that point. If it's a 100 watt light bulb then its emitting 100 watts as heat.

 

[everman]

As already stated it will be radiated as heat energy. However what I think he really intended was what would happen if the interior was a mirror surface, which I think would have similar results.

 

[Bobthelost]

Originally posted by: everman
As already stated it will be radiated as heat energy. However what I think he really intended was what would happen if the interior was a mirror surface, which I think would have similar results.

Yep, so let's play with the mirror idea instead.

Mirrors aren't perfect, each time the light bounces off the mirror a tiny bit of energy is lost. Which means the mirror heats up. Eventually the mirror would get so hot it would melt. Assuming the bulb fillament itself doesn't get so hot it burns up first of course.

 

[Auryg]

Originally posted by: Bobthelost

Originally posted by: everman
As already stated it will be radiated as heat energy. However what I think he really intended was what would happen if the interior was a mirror surface, which I think would have similar results.

Yep, so let's play with the mirror idea instead.

Mirrors aren't perfect, each time the light bounces off the mirror a tiny bit of energy is lost. Which means the mirror heats up. Eventually the mirror would get so hot it would melt. Assuming the bulb fillament itself doesn't get so hot it burns up first of course.

So what would happen in a perfect mirror? With an indestructable filament?

And what's the difference between something that's pure white and a mirror? They both reflect all light, right?

 

[bobsmith1492]

White would diffuse the light as it reflected it... a mirror would direct it away at the same angle as the incident angle.

And there's no way to know what would happen with a "perfect" mirror; the energy would be absorbed SOMEWHERE. The air/whatever molecules inside would absorb energy, which would then transfer via convection to the surface, heating it up. If it were a perfect vacuum with perfect mirrors, the filament would absorb the energy and heat up, conducting the energy out through its attachment. However it may happen, somehow, 100W would be escaping somewhere. All you might be able to do is increase the thermal resistance from the filament to the ambient environment, in which case it would get realllly hot as it was dissipating 100W. Hypothetically speaking, nothing interesting would happen.

 

[Calin]

The filament would cool itself based on convection, and the hot air/gas inside will transfer heat (convection) to the walls.
Assuming there is a complete void, and only radiation moves energy in the bulb, you have a situation like this:
the filament pumps out energy as radiation. The radiation will reflect on the mirrors/walls, and will hit back the filament. Now, for a certain temperature of the filament, there will be a "radiation equilibrium" inside the bulb. (assuming you start to cool the filament using a different method, the radiation energy from the bulb will heat the filament back).
If you continue to pump energy inside, the temperature of the filament will grow, and so the "density" of radiation energy in the interior volume of the bulb.

 

[Octavarium]

Theoretically, if you have a perfectly inescapable source, with a perfect mirror and a perfect vacuum and a perfectly indestructible filament.... it would continue to get hotter and hotter. And hotter. At least, I think.

Realistically, with the same conditions.... you turn off the lights to go to bed and it's all cool.

 

[theslickvik]

depends on the type of paint

 

[WildHorse]

Fun question!

With a hypothetically PERFECTLY reflective mirrored interior bulb surface and a PERFECT vacuum inside the bulb and a PERFECTLY indestructible filament,

I think everybody here concurs in these first few steps:

Electrons within the filament will continuously cycle from lower to higher to lower energy states as
the inflowing electricity continually pumps filament electrons to higher valences momentarily,
the electrons then collapse to lower valences and emit light as they hop down to a lower energy level,
that light will hit the reflective inner bulb wall,
and in direct response to the OP, QUOTE: In theory, wouldn't it 'fill up' and then eventually explode? END QUOTE, the answer is "no" because conservation of matter/energy would prevent any "mass" of emitted particles from exceeding that of the filament.

But then everybody does not concur on next events. My conjecture:

The photons will impart some of their energy to atoms in the reflective surface, pumping their electrons to higher valences.

Those electrons of atoms in the reflective surface will hold the added energy only momentarily, then collapse to lower valences, emitting the energy as perhaps heat and/or other radiations, to the entire apparatus, both filament and envelope. This will mostly be as heat.

The heat will diffuse throughout the bulb, but will tend to preferentially radiate outward away from the bulb toward the relatively cooler exterior atmosphere, seeking thermal isostasis, because the bulb's interior will be hotter, and will not absorb more heat.

Photons within the bulb, having given some of their energy to the reflector's atoms, will themselves step down in energy so as to no longer remain visible light, but something else in the EM spectrum of longer wavelength than visible light.

The whole thing could be useful to warm incubating chic eggs.

 

[WildHorse]

dup post removed. oops

 

[XZeroII]

The universe would implode upon said lightbulb creating a 'hawking hole' (Steven Hawking named it after himself) whereby all matter, energy and wheelies (Hawking must have been having some fun when naming that particle/energy thing) would coalesce into a giant (although incredibly tiny) mass of Picards (he's a Star Trek fan too). The Picards would clog the Hawking Hole, creating a buildup of unimaginable force that would...

or nothing would happen. I really don't know.

 

[Calin]

Thinking about it, I see now that you would have:
electrons emitted from the filament (just like in the amp tubes of the old days)
sublimation of filament atoms and their later condensation to the enclosure walls (just like would happen in very hot incandescent lights)

anything more? anyone having any idea of the really high temperature processes? If hot enough, the atoms will form a plasma

 

[randay]

Yes the light bulb explodes. Its the exact same concept as when you plug your ears with ear plugs, close your mouth and eyes, put a clothes pin over your nostrils and think really really hard for a while. warning: do not try that at home unless you are a trained professional.

 

[So]

With wave superposition, assuming a perfect mirror and a filament that converted 100% of energy to light, you'd have an energy storage device.

The question is, is there any limiting factor to the amount of energy it'd hold?

Edit: Oh, the photons would exert a small pressure on the surface, losing energy and heating up the mirror. Eventually it'd crack. Essentially, I don't think a perfect mirror 'computes'. If it did then I guess there would be no pressure from the photons, but that would mean that there was no conservation of momentum for changing the direction of the photons.

 

[sdifox]

So perfect first surface mirror plus indestructible filament, how about the actuall wall itself? If we also assume the walls will stand up to the abuse, most of the energy would be absurbed back by the filament since it seems to be the only place for it to go. So you got one superheated filament that would turn into plasma eventually, but then it is supposed to be indestructible, then it would be a black hole of a filament

 

[mozirry]

if you put a light in a paper box, no light will come out but it will eventually catch fire.

dont try this at home

 

[imported_Seer]

This reminds me of super conductors. It's pretty much the same idea:

super conductors conduct eletricity with 0 resistance (literally)
and
our perfect light bulb experiment reflects light forever without ever losing any energy or blowing up or something.

An interesting comparison...super conductors, however, are real. If you apply a voltage to a super conductor setup in a circular circuit, then the current will continue to flow for thousands upon thousands of years, even if you remove the power source.