When I was in highschool I was assigned a Physics project in which I had to design a diamond so that light would exit the direction it entered (note, was an easy project with simplified 2D “diamonds”). In the real world this is what gives diamonds their “fire”.
What I want to know, is it possible to cut a diamond so that the light will never escape? If not, how about the next best thing, it takes hours, or even years, for the light to escape?
if it is possible to accomplish a “forever cut” what would happen to the diamond as more and more light collected inside of it?
I don’t think it’s possible if you’re talking about refraction from just the exterior surfaces of the diamond.
But there’s been a lot of interest lately in engineering materials with an internal nanostructure such that they exihibit a “band gap” for optical frequencies. That is, because the structure of the material creates constructive or destructive interference it will pass or exclude a narrow band of light frequencies in a manner similar to the way transistors pass or block voltage.
In fact, it is even possible in theory to construct such a material so that a photon would encounter destructive interference in all directions so it would be trapped in the lattice indefinitely.
Is the speed of light slightly changed while passing through different media, but no matter how fast the media or your frame of reference are going, you will measure the same value for the speed of light through the particular medium??
Sure! It’s easier to use glass than diamonds, but you could achieve the same with diamonds. The easiest way to ‘trap’ light is to take an optical fiber, and make a loop out of it. Then the light will go round-and-round, till it dampens out. Or you could just take a piece of glass and put mirrors at the ends. The trick is to get it in there… but that could be achieved with some of the fancier optical amplifiers. I’m not sure how they work, but I believe that one uses a doped fiber, where you add energy from the outside to excite electrons, which get de-excited when the light passes.
In fact that’s how one makes lasers!
Well, the problem is that if no light can get out, then no light can get in! Remember that light paths are always reversible, so if the light can get in one way, it can also get out ‘the other way’. And even if you manage to make some kind of loop within the diamond, the light will eventually dampen. I have no figures here, but I believe that only very expensive (read pure) optical fibers can transmitt for more than a few km. My guess is that after a few (or maybe a few hundred) meters the light will have been absorbed by impurities in the diamond.
I think Popup’s got it mostly right, but in a practical world I don’t think it would be easy, maybe not possible to construct a perfect light loss item like this. As he peoperly notes, light can go back the way it came in, so for a crystal or a fiber optic with any scattering inside or light paths that allow retroreflect some light will come out the same way it got in. The only “optical diode” I know of that lets light only go in one way and not out the other is a Faraday Rotator, but that would violate your rule of a single device, and I still think it wouldn’t stop light going back out – multiple reflections are fonna scramble the polarization.
As for the optical fiber idea, take a scrap of un-protected optical fiber into a dark room and put a laser beam in one end. You’ll see the whole fiber light up with scattered light at the edges – not a majpor proportion, but it’s getting out through the sides.
In the real world, I think that if you wanted an efficient way to lose light you’d arrange to have absorbing medium around to sop up the unwanted photons, rather than letting them bounce around until they get the opportunity to come back out. That’s why laser light traps are often just metal boxes painted flat black, and why telescope tube interiors are painted flat black. One recipe I recently encountered recommended adding stuff to the paint to make the surface bumpy, so the light that reflected would have another chance to be absorbed before it went down the tube.
Theodore Sturgeon once wrote about an item like the one described in the OP – a crystal cut so that lighht went in but not out, trapped within the reflecting walls. He called it a “light pump”, and claimed that it made a room measurably darker. I don’t think it would work – you could as easily (and with as much justification) say that a Black Sofa placed in a room is a light pump, and makes a room measurably darker. (see the story “Microcosmic God”.)
HA! I saw Cal’s name and thought “Damn! He’s gonna post what I was going to post before I got a chance to post it. Again!”
But he didn’t!
The OP said
I doubt this is possible in the real world. However, a SF writer, Bob Shaw wrote a series of short stories (collected in a book called The Light of Other Days) about a substance called “Slow Glass” that does exactly what you’re talking about. Light goes in, and after some predetermined time (hours, days, months, years) comes out again. He spends about 150/200 pages dealing with all sorts of implications that the stuff would have on society. Great stuff!
I always wanted to read the “Slow Glass” stories, but I’ve never run across them. I keep hearing about them, but never see them. I think they’re the literary equivalent of the Yeti.
It could be because everyone gets the title of the fix-up wrong. Ahem…which is Other Days, Other Eyes, not “The Light of Other Days” which, as everyone knows is just one of the stories in the fix up. :rolleyes:
BTW: There’s a couple of copies of Other Days, Other Eyes (what a rotten title!) for sale here
From here (esp. note the bottom of the page), the critical angle for diamonds is 24.26 degrees. I.e., any angle greater than that from the perpindicular and you get “total internal reflection”.
Too many posts are assuming that light can pass thru diamond (or other media) forever unchanged. Sooner or later every photon will be absorbed. For clear media it’s more later than sooner, but absorbtion will occur. If the atoms later re-emit a photon, the direction will be unpredictable. And diamonds are not completely clear as well.
Also, even “total” internal reflection is not total. A few photons will escape at the boundary reducing the strength of the beam over time. If your light source is not collinear (a laser) the small differences in angle will build up and effectively result in random scattering.
It’s inconceivable that a light beam can bounce around a diamond for more than a few seconds. Cf. optical fiber distances (and times).
There was a similar thread a looong time ago where someone postulated a ball with a perfectly reflecting interior. The idea was that you shoot a few photons into the ball and close it up before they escape again, then you could reopen it, and no matter how much time had passed, the photons would still be in there. Anyway, that thread had a long discussion of how hard it would be to reach that kind of perfection. Wish I could find it…
