英语阅读理解及答案题6篇.docVIP

1. The Light of the Twenty-first Century 1. The word laser stands for “light amplification by stimulated emission of radiation”. To many people lasers are very mysterious but a laser is simply a device that produces a very strong light. The light from a laser is called coherent light because it is light that moves in only one direction. In contrast, incoherent light, like the light from the sun or a light bulb, moves away from its source in all directions, so its strength is very spread out. The light from a laser, moving in only one direction and concentrated in a narrow beam, is much stronger. 2. As soon as the laser was developed, scientists began thinking of practical applications for it. One of the earliest uses was to make extremely precise measurements of distance and speed. For example, the distance to the moon was measured to within a foot, and the speed of light was measured to within a thousandth of a mile per second. As time passed, many more applications for the laser were developed. 3. Some of the most important uses of lasers are in medicine. Lasers can be used in surgery to open and close incisions with no danger of infection. In eye operations, a laser can be used to reattach a retina and to prevent excessive bleeding of tiny blood vessel in the eye. Lasers are also important in the treatment of cancer. A laser beam can completely destroy a cancerous growth without leaving behind any dangerous cancer cells that could start a new tumor. More recently, lasers have been used to remove skin discolorations like freckles, age spots, and birthmarks. Some dentists have even started using lasers for painless treatment of teeth and gums. 4. Over the past twenty years, personal computers have brought tremendous changes to the home and the workplace, and many of the most important developments in computer technology are based on lasers. From laser printers (including the newest colon printers to technology by which whole encyclopedias of information can be stor