Metamaterials

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Royal
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Metamaterials

Post by Royal » Sat Dec 08, 2012 2:49 am

Will scientists ever be able to create an invisibility cloak, such as the one used by the alien Romulans to render their warships invisible in Star Trek? Some of the earliest steps have already been taken toward this difficult goal with metamaterials, artificial materials with small-scale structures and patterns that are designed to manipulate electromagnetic waves in unusual ways.

Until the year 2001, all known materials had a positive index of refraction that controls the bending of light. Howver, in 2011, cientists from the Univeristy of California in San Dieco described an unusual composite material that had a negative index, essentially reversing Snell's Law. This odd material was mic of fiberglass, copper rings, and wires capable of focusing light in novel ways. Early tests revealed that microwaves emerged from the materials in the exact opposite direction from that predicted Snell's Law. More than a physical curiosity, these materials may one day lead to the development of new kinds of antennas and other electromagnetic devices. In theory, a sheet of negative-index material could act as a super-lens to create images of exceptional detail.

Although most early experiments were performed with microwaves, in 2007 a team led by physicist Henry Lezec achieved negative refraction for visible light. In order to create an object that acted as if it were made of negatively refracting material, Lezec's team built a prism of layered metals perforated by a maze of nanoscale channels. This was the first time that physicists had devised a way to make visible light travel in a direction opposite from the way it traditionally bends when passing from one material to another. Some physicists suggest that the phenomenon may someday lead to optical microscopes for imaging objects as small molecules and for creating cloaking devices that render objects invisible. Metamaterials were first theorized by Soviet physicist Victor Veslago in 1967. In 2008, scientists described a fishnet structure that had a negative refractive index for near-infrared light.


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Royal
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Re: Metamaterials

Post by Royal » Sat Dec 08, 2012 2:52 am

Snell's law (also known as the Snell–Descartes law and the law of refraction) is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water and glass.


Refraction of light at the interface between two media of different refractive indices, with n2 > n1. Since the velocity is lower in the second medium (v2 < v1), the angle of refraction θ2 is less than the angle of incidence θ1; that is, the ray in the higher-index medium is closer to the normal. In optics, the law is used in ray tracing to compute the angles of incidence or refraction, and in experimental optics and gemology to find the refractive index of a material. The law is also satisfied in metamaterials, which allow light to be bent "backward" at a negative angle of refraction (negative refractive index). Although named after Dutch astronomer Willebrord Snellius (1580–1626), the law was first accurately described by the Arab scientist Ibn Sahl at Baghdad court, when in 984 he used the law to derive lens shapes that focus light with no geometric aberrations in the manuscript On Burning Mirrors and Lenses (984).

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Pigeon
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Re: Metamaterials

Post by Pigeon » Sat Dec 08, 2012 3:09 am

No doubt the day will arrive. It will make for a strange, paranoid world. (I don't foresee people becoming less evil)

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