NEGATIVE index of refraction..what is it exactly?

Question

seems very interesting; I know they are based in the transmition of metamaterials , wich have a negative permeability and permitivity or something, but I don't understand much... how come we can have a negative index without letting the velocity in the media be faster than light :/.
(No links pls , I'm too lazy for that :P)

thanks beq...I like pucca too :)
cw ...could you make an effort an remember it?

Answer 1

The refractive index of a material depends on how it responds to magnetic fields (quantified by its permeability) and electric fields (quantified by its permittivity). The refracive index is given by the square root of the product of these.

For normal transparent material, both are +ve, so this square root is real. For things like metals, one or the other is -ve, and the refractive index is imaginary (ie involves the square root of -1). These materials are opaque.

But for meta materials both are -ve. So the refractive index is once again real, but because these materials have odd behaviours the normal convention of using the +ve root for the refractive index is reverse, and a -ve is used.

Meta materials still slow light down, but some of the usual rules are reversed. For instance, the doppler shift is reversed and snells law works in the opposite direction.

Answer 2

Image light is a bullet, You are standing above a pool of water and you aim to shoot a fish in the water ahead of you at an angle downwards. The bullet will change direction and miss the fish because the component of it speed vertically and the bullet falls short of the fish. If you imagined the water had a negative refractive index when the bullet hits the water it is no longer traveling away from you but starts coming back towards you in the water. So when you shoot a fish in water with negative refractive index make sure you are not standing in it at the time. ;-)

Answer 3

There was a good article about this in one of the last 2 Scientific American magazine (I can't remember which one.) I has to do with changing the electromagnetic force/properties of the light.