88 Lasers-High

Lasers FOCUS Question How do the properties of lasers make them useful?

激光聚焦问题激光的特性是如何使它们有用的?

What Are Lasers? A doctor carefully seals off leaking blood vessels during surgery. A machine slices through many layers of fabric at once. A metalworker lines up two steel panels and bonds them securely together. All this work is done using lasers. A laser is a narrow, concentrated beam of light. Laser beams do not occur naturally on Earth. The lasers we see around us are the products of human ingenuity. They have unique properties that allow them to be used in a variety of ways. Word Wise An acronym is a word that is an abbreviation made from the first letters of other words. The word laser is an acronym that stands for Light Amplification (by) Stimulated Emission (of) Radiation.

激光是什么?一位医生在手术中小心地封住泄漏的血管。 一台机器可以一次切下多层织物。 一名金属工人把两块钢板排成一行，并把它们牢固地粘在一起。 所有这些工作都是用激光完成的。 激光是一种窄而集中的光束。 激光束在地球上并不是自然产生的。 我们周围看到的激光是人类聪明才智的产物。 它们具有独特的特性，可以以各种方式使用。 缩略语是由其他单词的首字母组成的缩写词。 激光这个词是光放大(受刺激发射)辐射的首字母缩写。

In Perfect Sync How does a laser beam differ from a flashlight's beam? Remember, light can travel in waves. A flashlight emits the full range of visible light waves, from red to violet. These colors have different wavelengths— the distance from peak to peak in a wave. When these different wavelengths travel together, they blend and produce a broad beam of white light that spreads and fades as it moves outward. By contrast, lasers produce light waves with the same wavelength that together make a single-colored, or monochromatic, beam of light. The light waves are synchronized perfectly. They form a highly focused beam of light that can travel a great distance without fading.

完美同步激光束与手电筒的光束有什么不同? 记住，光可以以波的形式传播。 手电筒能发出从红色到紫色的全范围可见光波。 这些颜色具有不同的波长，即波峰与波峰之间的距离。 当这些不同波长的光一起传播时，它们会混合在一起，产生一束宽阔的白光，随着向外移动而扩散和减弱。 相比之下，激光产生波长相同的光波，这些光波合在一起形成单色或单色光束。 光波完全同步。 它们形成高度聚焦的光束，可以传播很远而不褪色。

Making a Laser Beam Creating a laser beam is exciting— literally. A medium— a substance that is usually a gas— is placed in a chamber called a resonator. The chamber has mirrors on opposite sides. A burst of electrical energy passes through the medium. The energy causes the electrons in the medium's atoms to become excited and move faster. When the energy is removed, the electrons slow down. As they do, they release light particles called photons. Energy is switched on and off very quickly to make the electrons speed up and slow down many times. The electrons keep producing photons as they change speed.

制造激光束确实令人兴奋。 一种介质——一种通常是气体的物质——被放置在一个叫做谐振器的腔室中。 这个房间两侧各有一面镜子。 一束电能通过介质。 这种能量使介质原子中的电子被激发并移动得更快。 当能量被移走时，电子的速度就会减慢。 在此过程中，它们释放出一种叫做光子的轻粒子。 能量被快速地打开和关闭，使电子多次加速和减速。 电子在改变速度时不断产生光子。

The photons collect in the chamber, bouncing back and forth between the mirrors and moving even faster. Eventually, a stream of photons shoots out from the chamber through one of the mirrors. Scientists presented the scientific theories that are the basis of laser technology in the early 1900s. At first, they had little idea of how lasers might be useful. It wasn't until 1960 that the first laser was constructed. By 1961, a medical laser was used at a hospital in New York City to destroy an eye tumor. From that point on, the use of lasers grew, not just in medicine but also in other fields.

光子在腔室中聚集，在镜子之间来回反射，移动得更快。 最终，一束光子通过其中一面镜子从腔室中射出。 20世纪初，科学家们提出了激光技术的基础科学理论。 起初，他们对激光的用途知之甚少。 直到1960年，第一台激光器才被制造出来。 到1961年，纽约市的一家医院使用医用激光摧毁了一个眼睛肿瘤。 从那时起，激光的使用越来越多，不仅在医学上，而且在其他领域。

Cutting-Edge Technology Lasers are pure light energy. A laser beam by itself is not hot. It can generate heat, however, if it hits a material that can readily absorb its light energy. The beam's sharp focus creates a point with enough heat to vaporize, or remove, the material in that spot. This property makes a laser beam a useful cutting tool. In medicine, lasers are especially useful as surgical instruments. They can get to hard-to- reach places better than other cutting tools. Tumors that are otherwise inoperable can be burned away. Because it is easy to direct the laser, doctors can avoid damaging healthy tissue. Lasers are often used in delicate operations on eyes. Safety! Lasers can hurt as well as help eyes. A laser beam raises the temperature of the surface it hits. Laser pointers aimed at the eyes can cause temporary or even permanent loss of vision.

激光是纯光能。 激光束本身是不热的。 然而，如果它碰到一种能轻易吸收其光能的物质，它就能产生热量。 光束的锐利焦点产生了一个点，有足够的热量来蒸发或去除该点上的物质。 这种特性使激光束成为一种有用的切割工具。 在医学上，激光作为手术器械尤其有用。 它们能比其他切削工具更好地到达难以触及的地方。 否则无法手术的肿瘤可以烧掉。 由于激光很容易引导，医生可以避免损伤健康组织。 激光常用于眼部精细手术。 安全!激光可以帮助眼睛，也可以伤害眼睛。 激光束会提高它所击中物体表面的温度。 瞄准眼睛的激光笔会导致暂时甚至永久的视力丧失。