Pointing and focusing a laser beam on a target that is rocketing skyward at thousands of miles per hour is no easy task, but the Airborne laser is uniquely able to do the job.

对于飞行速度每小时数千英里的目标进行激光束瞄准和聚焦并不容易，但机载激光器是唯一能够完成这项工作。

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In other words, ultrasound essentially travels in a very narrow beam — this makes it great for focusing the waves toward a desired area, but not for actual aural comprehension.

换言之，基本上超声波的传播声束极窄，这非常有利于将声波集中至指定地点，但对实际听力则无所助益。

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A team of physicists in the us has created an infrared laser beam at a point in mid air, by focusing a UV laser onto a tiny volume of oxygen molecules.

美国的一个物理学家团队通过将一束紫外激光聚焦于一小块氧分子中，发明了一种聚焦于半空中一点的红外激光束。

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She is working on focusing the transmitted beam into a much smaller area, so that less energy is lost along its way.

ECONOMIST: Archaeology