Slashdot Mirror
Negative Index of Refraction Created
FortKnox writes "Scientists studying how a new composite material reacts with microwaves have found that the waves refract in a way the defies a law of physics. The physical formula states that the wave will refract a specific way, but passing through this new material, the wave bends in the exact opposite direction. Scientists believe this is the first demonstration of a negative index of refraction." I haven't been able to find a more scientific report about this - if you find a link, please post the link below.
Thank you!!! As to the phase velocity going faster than the speed of light, here's an analogy that may help people understand why this isn't the same thing as FTL travel: Imagine you have a laser pointer. A really bright laser pointer. You point it at the wall, and you can see a little red spot of light on the wall. You then quickly tilt your hand, and the spot moves. The velocity of the spot might be around 30 miles per hour, depending on how fast you tilted your hand and how close to the wall you were. Now point it at the moon. It's a really strong laser pointer, so now there's a little red spot on the surface of the moon. Quickly tilt your hand a little, and the spot races across the surface of the moon at an amazing velocity. (I don't know how far away the moon is; if it isn't far away, then suppose we're talking about a moon somewhere in another galazy.) So, with a bright laser pointer directed towards a far-off object, you can create a spot of light which moves faster than the speed of light. But this is not the same as transporting *information* or an *object* faster than the speed of light. - Kevin
The right hand rule is not really a rule, it is a easy way to remember the direction of the positive cross product of two verticies. Its the same as putting your hands in front of your face to see which one forms an 'L' for 'Left' hand.
So tell me how these materials form a negative cross product of radiation across the E and M flow?
And what does this have to do with refraction?
No links to anything. You should be...
..proud of yourself. Fooled the moderators again.
~^~~^~^^~~^
This is what I was thinking to. I might be missing something here but isn't this almost certainly going to happen in the case where you have a substance through which microaves travels faster than they do through the atmosphere?
sigs are a waste of space
that's not quite it. that would simply give a less than 1.0 IOR.
I wonder if POVRay will let me simulate a negative IOR? I wonder what that looks like? Time to whip out the gratuitous checkerboard floor!
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
The paper by Shelby et al. is here, but I belive full access requires a subscription. (Most universities have this.) Wiltshire has a less technical Perspective in the same issue.
Bob
With negative index of refraction you are able to recreate the source field at some other "image" position. That means no resolution limits set by the wavelength of the light and and focusing power (usually called numerical aperture) set by the lens. Note that the negative refraction lens conjugates the phase of the wave. For a plane wave, it just looks like the wave reverses direction at the other side of the (flat) lens. For a spherical wave originating at some point, the conjugated wave will focus onto a point on the other side of the (negative refraction) lens.
For antenna research this will probably mean really a lot. Most probably we will also be able to locate sources of (microwave) radiation with great precision.
/jarek
There are two types of equations in physics. There are fundamental equations and derived equations. Fundamental equations are purely empirical beasties, whose sole justification for their existance is that they match the data that science produces when you plug numbers into them. In theory there are only two equations that are properly empirical, the general theory of relativity and the standard model of physics (in practice there are a few more physical phenomena whose underpinnings are not well enough understood to be linked to those two equations).
Then there are derived equations, like the special theory of relativity and the various laws concerning the index of refraction. These equations have certain conditions and assumptions built into them and it is possible to come up with phenomena that seemingly defy them because you're breaking the assumptions they're founded on. A nail sticking to a magnet defies the law of gravity, but that's only because the law of gravity by itself assumes no other forces in action, for example.
So in short no laws of physics were broken by this. No doubt some aspects of quantum mechanics were used to undermine what is effectively classical physics.
The scientists did NOT violate the laws of physics.
<p>
They found a substance in which low energy wavelengths will travel faster than the speed of light in air. This is different than the speed of light in a vacuum, which is a constant and would really screw things up if discovered false.
(These 1930's physics books are loads of fun.)
"Reactionaries must be deprived of the right to voice their opinions; only the people have that right." - Mao
Thbbbt.
If they're not going to make the next Furby or Tickle-Me Elmo with what they discover, why should they keep getting research grants?
"Reactionaries must be deprived of the right to voice their opinions; only the people have that right." - Mao
As for previous articles on this, IEEE Spectrum ran a story on this in January. If you have an IEEE account (or know someone who does) then you can see it here. This is a short "news in brief" style of article, but it still does a reasonable job of explaining the effect. The thrust of the article was actually about the potential use of this effect in semiconductor lithography (used for printing ICs).
Spectrum also references the original paper on this effect, which appeared in Physical Review Letters last October. This paper was written by John Pendry from the Blackett Laboratory at Imperial College, London, UK. His work was preceded by David Smith and Sheldon Schultz at the University of California when they built some of this so-called left-handed material using a "metamaterial". In fact, the theoretical background for left-handed material has been around since 1968 when the Russian physicist Victor Veselago first looked at it.
So this material has been around for a little while now. You just have to know the right places to look. :-)
Me and my lab partner came up with a negative index of refraction in a Physics lab in college. It was at that point that I realized that I should change my major from Physics to Computer Science.
Software sucks. Open Source sucks less.
Um, yeah, what the other guy said. Scroll around in here and you'll find links to Nature (which is eminently more respectable than Scientific American), and that article notes that the research will be published in Physical Review Letters, which is a pretty damn solid place. I mean, it hasn't been independently duplicated yet, but it has gotten coverage in the "real" scientific press- Nature is not about to go spouting off unless they feel it is pretty solid. Those with mod points should feel free to mod the parent down.
~luge
IAAL,BIANLY
This isn't really against the laws of physics of course :) Basically if you've ever done any electromagnetism then you'll have heard of the right-hand rule which governs the interactions of the electric and magnetic fields and the directions of their wave velocities. But for this new class of composite materials we instead get a left-hand rule, meaning that Snell's law (which governs the change of angel caused by the change of velocity of EM radiation through materials) is essentially reversed...
The really unusual thing about these materials is that they exhibit negative electric permittivity and negative magnetic permeability, never seen before in any material. There are sure to be plenty of interesting applications to follow.
OK Mr. Cochrain, April Fool's Day is over.
If tits were wings it'd be flying around.
Actually, that's backwards. Making perfect spheres and parabolas is hugely easier than making an optical flat. There's a reason why amateur scope makers usually will grind their own primary mirror, but buy a secondary.
If tits were wings it'd be flying around.
Fiberglass and copper, eh? Well, how about the fiberglass REFRACTING it in the PROPER direction, and right after the copper REFLECTS it exactly the other way????
--
I understand your sentiments, but don't forget that the laser was sat around in research labs for a decade or so before anyone thought of a use for it.
Now, I personally own two (one in my CD-ROM drive, one in my audio CD player).
As DeadInSpace said, don't knock it just because it doesn't appear to be useful now. You never know what we might think to do with it in the future.
Cheers,
Tim
It's official. Most of you are morons.
Are you saying you've gotten pulled over because the officer noticed red shift? That's pretty damn fast.
Photos of bits of the past hiding in the present: afiler.com
Looks pretty much like a flat sheet would cause divergent rays to be straightened toward parallel. That would be quite useful, since it's loads easier to make something perfectly flat than perfectly curved
********* sig: If you don't like the law, get filthy stinking rich, and buy a better one.
can be found at Science Magazine.
Light also refracts when going (for example) out of glass back into vacuum. So it does indeed accelerate back up to full speed once it leaves the glass. There's nothing mysterious about going faster than lightspeed - different materials have different lightspeeds. You just can't travel faster than the speed of light in a vacuum.
--Ben
(Here in California we've got much smaller molecules.)
--Ben
For the refractive index to be negative, doesn't that mean that the speed of light through this medium has to be *higher* than through a vacuum?
I'm confused..
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
No, fats are made of fat (lipid molecules) -- think grease and oils. No water in 'em. Nothing magical about water -- it's just that there's water in just about any kind of food you put in a microwave, and water reacts pretty strongly.
--
+1 Insightful, -1 Troll. What can I say, I'm an Insightful Troll.
to my mind you cannot ever break the laws of physics...only your ideas of what the laws of physics are can be wrong.
Quidquid latine dictum sit, altum viditur
What are the implications of this technology for satelite dishes? Can they be made smaller, cheaper, or am I trying to find a use for this technology way too early?
-bugg
bzzzzzt! Try again.
Cooking microwaves run at a frequency of 2.45 GHz, which is a wavelength of 12cm. Water molecules are significantly smaller than 12cm. ;-)
There are a number of rotational and (to a lesser extent) vibrational water transitions around 2.45 GHz which get smeared into a band in liquid water. The molecules absorb the microwaves to get into excited rotational states, and then collisionally de-excite during collisions with other molecules, thus distributing the energy into kinetic energy of the entire food.
[TMB]
Having just completed a Ph.D. in this field I can say with some certainty that negative indexes of refraction are not new.
The relative dielectric constant of a plasma (cold, unmagnitized, above the ion plasma frequency) is:
1 - wp^2 / w^2
where w is the frequency and wp is the plasma frequency. Below the electron plasma frequency, the dielectric constant of a plasma is negative. (Actually, part of my thesis addes terms to handle electron pressure and density gradient effects.)
Hell, Rayleigh (think 1900s) was using such treatments to calculate resonance frequencies for things like the sun (wp/sqrt(3) by the way).
What was somewhat new about the research referred to is they simultaneously created negative dielectric constant and a negative magnetic permeability.
However, the techniques they used to do so have been around since the 1950s and form the basis of all sorts of electron devices like traveling wave tubes (a staple of satellite communication).
Kevin
"Scientists studying how a new composite material reacts with microwaves have found that the waves refract in a way the defies a law of physics.
Somehow, I doubt it. The article headline says the same thing. The material doesn't defy anything, our knowledge of the laws is just lacking. It's a nitpick, but it's silly to say it defies the law.
The Good Reverend
I'm different, just like everybody else.
Is that air or vacuum? It's been a while since I've taken Physics so I don't remember whether refractive index is defined with respect to air or vacuum - i'd be surprised if it was the former.
What it seems to me is that they have discovered a material where the waves travel faster than the speed of light in vacuum (hence they refract the other way). That would be a quite interesting discovery if that was the case.
Mmmm.. Donuts
> These modern kids don't know the simple
:-)
> joy of saving four bytes of page-0 memory
> on a 6502 box.
Actually, I do
And, I would probably fall under the category of "modern kid".
So there!
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Does this mean that I won't be able to fry ants with a magnifying glass made out of this stuff?
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Just a detail here: as far as I understood this, the refraction index is not negative, it is smaller than 1 (0n1), so it has the opposite refraction effect as most materials.
Opus: the Swiss army knife of audio codec
The big deal is the difference between two different kinds of speeds of a wave. The wave's group speed is the speed at which the wave energy moves. What determines refractive index is the how a material influence waves' phase speed, an entirely different beast.
Phase speed is the speed at which wavefronts move through the medium, and it isn't limited by the speed of light. A techie example of a phase speed is the speed at which text scrolls across a rolling LED sign (we've all seen them). You can make the text scroll as fast as you like, in principle, because individual LEDs don't have to communicate with one another -- they just turn on and off at set times. You can even make the text scroll faster than light!
Phase speed and group speed are the same in nondispersive media (that is to say, when all wavelengths are propagating at the same speed). In air and vacuum and the like, that's approximately true. But in a dispersive medium, where propagation speed depends on wavelength, they differ. An example of dispersive wave propagation is the motion of ripples on the surface of water. If you throw a stone into water and watch the individual ripples move, each tiny ripple forms behind and overtakes the overall ring of ripples, growing to a large size in the middle and then shrinking again as it gets away from the pack. The tiny individual ripples are following the phase speed, but the energy only propagates across the water as fast as the overall ring of ripples.
How is this related to negative index of refraction? Most materials reduce the phase speed of light, and hence have a positive index of refraction. But spatially coherent structures can have the opposite effect and raise the phase speed above C. You see the effect in microwave waveguides (pipes for steering radio waves) and in radio scattering through of coherent arrays of antennae. You also get it, albeit with much shorter wavelengths, in crystallography -- most crystals have a negative index of refraction for X-rays, as the crystal planes form waveguides for the short wavelengths.
To be honest, from the Reuters writeup I don't know what the big deal is or why UCSD issued a press release at all. Clearly we're not getting the whole story.
There was an article on Economist a while back about how a material with negative refractive index may make a perfect lens, one which the diffraction limit is overcome, etc.
See my post for a link to an article as to how a material with negative refractive index may lead to making a "perfect lens"
Personally I want to use this to create a temporary wormhole at the bottom of the bar's tap. Now this would be a partial wormhole (perhaps by size or perhaps find some way to having it have a very low mass threshold) Basically the other end would be at the bottom of my mug (to prevent over foaming). Perhaps by creating several of these across the bar I could siphon off of many sources. I would have a literal bottomless mug. (unless they switched locations on the tap I suppose...). Man, that would be a great way to make a black and tan. On the other hand, why put the entrance point on a tap, just put it in the keg. That way I don't depend on both my activation of my end, and the barkeep filling (not really) some other customers brew up.
I seek not only to follow in the footsteps of the men of old, I seek the things they sought.
I tried to draw a picture of what the light path would look like, but the ASCII art set off the lameness filter. :-(>
Imagine a waist-high block made of a material with a negative IOR, and assume it's transparent (yes, opaque materials still have an IOR). You fire a laser from your hand at some point on the block in front of you. When the light refracts, it actually refracts back toward your feet, rather than the far side of the block.
... but it takes a score 2 reply with a different subject for any moderator to realize it :-)
The evaluation of an action as 'practical' . . . depends on what it is that one wishes to practice.
I knew that this seemed awfully familiar.
"
on which the university has applied for a patent.
"
This is physics, the patent will cover the material in question.
If it was software, it would cover the concept of negative refractive index.
In the case of physics, other people are free to figure out how to make other materials with a negative refractive index, with one click - noone is allowed to figure out an alternate implementation.
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. (Einstein)
The velocity of light in a vacuum is fixed.
It may change it's energy / frequency but not it's velocity.
From the point of view of a stationary observer on the event horizon of a black hole all infalling light is blue shifted an infinite amount - serious suntan lotion required. From the point of view of an observer at infinity looking at a light source on the event horizon it's inifintely redshifted - the light has no energy.
However, it's still travelling at the speed of light in a vacuum in both cases.
You can bend space, you can warp time, you can't change the speed of light.
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. (Einstein)
Or red shift if you're travelling away from the officer who then radios his mate to pull you off.
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. (Einstein)
setend PREREQUISTIE=understand_difference_between_phase_a nd_group_velocity_(2nd_year_physics)
I think it's only the phase velocity that is reversed - not the group velocity. Since the phase velocity is frequently above the speed of light anyway I can't see this being a problem.
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. (Einstein)
n the index of refraction is the speed of light in the medium v divided by the speed of light in vacuum c.
n between zero and one would mean that light is traveling faster in the medium than in vacuum.
A negative index doesn't really make since in the same way. I would assume that in this special case |n| is greater than one and that the reflection about the axis is caused by some optical effect not having to do with the speed of light.
No. They've discovered a material where a wave entering it travels in the reverse direction when in the material than it entered or when it leaves.
You'd expect that that would mean that waves would get reflected but if you do the maths or think about the wave on the boundary of the material you find that that's not the case... anyway that's the best I can explain it in laymans terms.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Hmm. Either I had a login and I didn't know it(!) or they've just discovered that they'd left password protection off the page... anyway I can't access it anymore.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Check out the following link to a PDF file:
Physical Review Letters
Warning: probably don't bother if you haven't studied Maxwells equations... definitely don't bother if you haven't heard of Maxwell's equations!
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"cmstremi
;-)
>How will this help me pick up chicks?
It won't. They will have better binoculars and be able to see you coming from miles away. It should help them find me though
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"http://www.afrlhorizons.com/Briefs/0001/SN9912.htm l
Pretty technical stuff but check it out.
"I think you know what I'm talkin' about, Mr. President; We're gonna kill us a mummy!" - Bruce Campbell as Elvis Presley
I'm not so sure about this claim, and find it interesting that there is no corroborating evidence elsewhere on the net (I tried, believe me). If this isn't "Cold Fusion II", then Sheldon Schultz has some explaining to do. Why is this not published in the Scientific American?
I suspect we will read about it in the paper tomorrow, and there will be an Entertainment Tonight feature on it later in the week. What ever happened to responsible journalism and scientific inquiry?
Hype alone will not change the laws of Physics. Although it is true that light will bend according to the refractive index, it is the angle itseld that determines the index of Refraction, if I recall correctly. Therefore, light will bend one way when going from air into glass, and another when going from air into a vacuum. So which way does light go here? If it goes from a vacuum into the medium in the same way it would go from air into a vacuum (or glass into air, i.e., from a higher to a lower medium), then, okay, you have something there. But why doesn't the article bother explaining the phenomena?
It reminds me of that article wherein they claimed that they found something that travels faster than the speed of light. I am still somewhat dubious on that, since it is only infomation that has passed out of that medium faster than a light beam would have traversed the medium, but not the initial pulse: that was absorbed, I believe.
Of course, I am just one guy. I could be wrong here. But not about the dearth of explanation...
SDMI: Finally! Music that won't rip or burn! Brought to you by the fine folks at RIAA.
Ok, I think someone already mentioned that if the real part of the index of refraction (n) is less than one than light goes faster than c. The speed of a single frequency is equal to c/n. This however is just the speed of a single frequency. If you send a pulse through you will find that dispersion will slow the pulse down meaning that the pulse will ALWAYS travel less than c (pulses are made of many frequencies -- the frequencies travel at different speeds this slows down the entire pulse.) So yes a single frequency can travel in material (many metals for example have indices less than one but the also have high imaginary parts of the index of refraction which means there is a high amount of absorption.) But you can never send information faster than c so this doesn't break any laws of physics. The article wasn't very technical so it is hard to say but I imagine that there is some non-linear effect that is causing the light to bend in a strange way. I'd have to read the original article to see what is going on.
What exactly would "negative" refraction look like? This sounds like a very late April fool's.
kha0S and Dr. Zowie have provided the most correct explantion so far.
a )
NatePWIII is incorrect for what is being discussed here, these materials are not less dense than air.
Materials that we are talking about are left-handed and semi(?)-left-handed. True left-handed mediums have both a negative permittivity and permeability. There are other materials that are not truely left-handed, some ordinary metals such as copper and silver have negative permittivity (still +'ve permeability) at optical frequencies.
As kha0S said these mediums behave exactely opposite that of right-handed mediums (in the sense of vectors E,H,and B). But Snell's Law isn't reversed, it becomes complex and hence describes change in the phase of incident waves.
Snell's law :
sqrt(epsilon1)sin(theta)=sqrt(epsilon2)sin(thet
So if permittivity (epsilon)is -'ve the sqrt()'s make the relation complex, ie. a+jb. This implies that the materials affect the phase of an incident wave. This agrees with what Dr. Zowie said, as phase velocity is defined as:
v = sqrt(permittivity * permeability)^-1
I'm not sure what happen with a true left-handed material (reversed vector characteristics but no phase change?), but with semi-left-handed material you can see that the phase velocity becomes complex also.
I hope this clarifies what kha0S said somewhat or makes any sense at all. There are still many other thing going on in these materials. A more complete explanation lies in how evanescent waves, EM field component that die away exponentially within a wavelength of their source, interact with conducting electrons in the materials we are discusing.
If I'm wrong please correct me. If you want more information look up the following researchers:
Sheldon Schultz (UofCal, San Diego)
David Smith (UofCal, San Diego)
John Pendry (Imperial College, UK)
Victor Veselago (Russian Acadaemy of Science)
- remove the primate to mail
Check out the Vinny the Vampire comic strip
"It is a greater offense to steal men's labor, than their clothes"
At least not in the way people mean when they talk about breaking them.
Physics - indeed science in general - is basically a collection of so-far not disproven hypotheses - which are based on observation, experimentation and logical (mathematical) deduction.
There are no immutable 'laws' - there are only hypothesis for which no exception has been found.
It's actually really important that scientists don't think in terms of 'laws' - because most major leaps forward occur due to someone 'breaking' then re-inventing one of these laws. Or put it another way - we come across these observations which don't fit the hypothesis so we have to ask 2 questions
1) are the observations correct?
2) is the hypothesis correct?
If we think in terms of unbreakable laws we'll throw out Question 2 at the beginning.
Fortunately most scientists don't talk in terms of laws - it's a popular science term.
An anti-rainbow? That would be an interesting experiment in art class.
It would interesting, except to be an "experiment", you'd have to get an art class to follow the Scientific Method, including formulating a hypothesis, falsifiability, etc.
Ummm. Yeah. Cough.
How will this help me pick up chicks?
Ok my physics is pretty rusty but I always thought that the reason for light bending between mediums was that the light slowed down going from the less dense medium to the denser medium. Does this mean that the light accelerates when it goes into this new substance and if so is the light then travelling faster than light?
Slashdot: Proof that a million monkeys at a million typewriters can create a masterpiece
"Yeah, the speed of light sucks."
-- John Carmack, Wired 4.08, p. 189
"And like that
One time, we were driving to a nearby mall. Two maps said that Bent Tree Drive made a sharp left curve. We're tooling along, looking for the sharp left curve so we know there's only two more miles to go.
Well wouldn't you know it? Bent Tree Drive has been under construction for a month. The sharp left curve is now a sharp right curve, followed by two sharp left curves.
There's an old saying: "Two wrongs don't make a right, but three rights make a left." It had nothing to do with this.
Anyway, it's a good thing I was behind the wheel paying attention. Had I been expecting the sharp left curve, I would have driven the Cruiser into a lake. Fortunately, I made the right followed by two lefts and we all got to the mall safely.
In my humble opinion, something similar has happened to these scientists. Perhaps the prism was under construction. Maybe they didn't see the tiny detour signs or maybe some kids snuck off with them in the middle of the night. You know in the Road Runner cartoons when Wile E. Coyote turns the sign around? I'll bet that's what happened here.
In fact, I understand the scientists also painted a tunnel on the side of a mountain and the microwaves went right into it. See? That's exactly what I'm talking about. If they're really smart, they'll watch out for the oncoming train. It would be a shame if the train hit them and squashed them flat against the front before they could collect their Nobel prize.
Got a full tank of hot grits and a penis bird in the glove box.
While here is the full research article in science magazine.
Both of these require a subscription, but you can read the abstract without paying.
I couldn't find anything directly about the microwave refractor, but a search for "negative index of refraction" turned up three short pieces on the basic physics: 1 2 3.
Note that these involve putting conductors into the near field of the emitter -- that means within a fraction of a wavelength of the light source or microwave antenna. But to me, that just makes the metal an added piece of the antenna, and one well known directional radio antenna uses an array of metal rods in the path of the emitted waves...
I don't know if the rings and fiberglass arrangement is just a variation of this.
When something strange is discovered (something previously often considered impossible), does it really matter if there isn't a use for it this very moment?
No.
If every discovery with no apparant use was treated the way you react, portable computers running at 1,000,000,000 Hz weighing less than 3kg would not exist today, just to name something. What if no-one ever tried to research and understand radio-activity (which would not seem very useful at the time), would we have the ability to take X-rays today? Or to try and cure cancer with it?
Scientific discoveries will almost always be of significant use, and should be treated as such. Even when there doesn't seem to be an application yet.
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Theoretically, a negative index of refraction could be used to bend space time, and create a region oof negative energy strong enough to keep a wormhole open and allow us to traverse great distances in space and time. I have written a paper on this which appeared in the Quantum Mechanical Review some months ago, and I am very excited about it.
I am currently looking for funding to begin the first tentative steps of building a Faster Than Light warp drive. Of course, it will not be completed for some time, and will have some difficulties, but I have already, under laboratory conditions, excited a small lump of cheese to 60% light speed (I chose cheese because it is organic and therefore can show what would happen to the human body).
Hopefully, all Mankind will benefit from this discovery, and we can approach our destiny in the stars.
I want to touch the Godhead. As a physicist, I think it is possible with negative refractive indices.
The article actually talks of a negative refractive index.
Refractive index is defined as c/v where c is speed of light in vacuo, and v is speed of light in material.
A negative refractive index implies that when light hits the boundary from one side, it is also approaching the boundary from the other. Needless to say that this would have all sorts of problems with causality.
What's probably implied is that the refractive index is less than 1. This is actually fine, but it does not imply the signal in the material is faster than light.
Sound odd?
Refractive index is based upon the 'phase velocity' which does not have to be the same as the 'group velocity'. Imagine a little packet of waves. The group velocity is the speed of the packet - this can't be greater than c. The phase velocity is the speed of the wave peaks within that packet.
If you imagine travelling along with that packet of waves, the waves would appear at the back of the packet, grow, and die away at the front. The peaks travel faster than the group, but no information beats the group.... Einstein can rest easy. (This only happens in summat called a dispersive medium by the way, i.e. anything where wave speed depends upon freq, and it happens because a wave packet, being other than a pure sine wave contains a range of frequencies which travel at different speeds giving a sort of beating effect)
Materials with a refractive index of less than 1 are well known. For example, there is a famous Pink Floyd Album with a prism on the cover.....
--
Murky
Murky
A wannabe geek with no money to geek with.