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  3. Researchers announce that they’ve built the world’s first invisibility cloak. The device works only in two dimensions and only o

Researchers announce that they’ve built the world’s first invisibility cloak. The device works only in two dimensions and only o

admin2009-04-23  50
问题     Researchers announce that they’ve built the world’s first invisibility cloak. The device works only in two dimensions and only on microwaves.
    "The concept that you can cloak something and make something invisible can now be demonstrated," said Duke University physicist David R. Smith. "This is the first time where we show that you can actually take electromagnetic waves and wrap them around some region that you want to conceal and restore them on the other side."
    An uncloaked object would cause an interruption in the waves, creating a "shadow" behind the object. But the cloak succeeded in making the waves reconnect on the other side.
    The electromagnetic sleight-of-hand(巧妙的手法)is enabled by novel, human-made substances called metamaterials. "Using these materials, you can create a field-region in space where no electromagnetic phenomena penetrate," said team member Sir John Pendry, a physicist at England’s Imperial College London.
    Researchers say the new technology could aid antenna and radar designs—not to mention obvious military applications, like hiding spy planes or even buildings. But scientists have a long way to go. The new, experimental cloak measures just 5 inches (13 centimeters) wide and 0.4 inch (1 centimeter) tall. To make it work, researchers painstakingly tuned the design of the cloak’s metamaterial parts so that incoming microwaves slipped around its inner surface.
    Schurig and his colleagues say their cloak created a space nearly, but not completely, invisible to microwaves. The device still generates a minute reflection and shadow.
    Experts say the breakthrough will certainly conjure(使出现) excitement. "Cloaking has been a long-time dream for many scientists," said Xiang Zhang, a metamaterials engineer and physicist at the University of California, Berkeley, who was not involved in the research. "If we look at these experiments, of course, it doesn’t give you three-dimensional, arbitrary shape cloaking," but the new cloaking device is significant nonetheless, he said.
    The team says their next goal is to build a spherical invisibility cloak that shields microwaves in three dimensions, a task they describe as vastly more difficult. But they are confident it can be done.
    While the general design theory has been worked out, metamaterial fabrication technology has yet to catch up. Researchers are still puzzling over, among other things, how to make metamaterials that work for light in the visible spectrum, which has smaller wavelengths than microwaves.
    Indeed, it may be impossible to build a cloak that can block all the colors found in the visible spectrum, the team says. "All technologies have problems, except when they’re magic," Duke University’s Smith said.
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答案electromagnetic waves
解析 由题干中的wrapping定位到文章第2段末句“...you can actually take electromagnetic waves and wrap them around some region that you want to conceal and restore them on the other side．”此处需要填入名词性成分，作wrap的宾语。文中wrap的宾语them指的就是前面的electromagnetic waves。
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