2. 外语
  3. A scientific discovery is often made 【C1】______ before someone is able to put it to use. 【C2】______ , scientists discovered how

A scientific discovery is often made 【C1】______ before someone is able to put it to use. 【C2】______ , scientists discovered how

admin2010-03-19  59
问题      A scientific discovery is often made 【C1】______ before someone is able to put it to use. 【C2】______ , scientists discovered how to split atoms decades 【C3】______ the invention of the atomic bomb and the use of 【C4】______  power to produce electricity. But sometimes discovery and 【C5】______ happen at the same time, as occurred more than thirty years ago 【C6】______ the discovery of coherent light and the invention of the laser.
     The word laser 【C7】______ "light amplification by stimulated emission of radiation." To many people, lasers are very mysterious, but a laser is simply a 【C8】______ that produces a strong light.  The light from the laser is called 【C9】______ light because it is light that only moves in one direction. 【C10】______ , incoherent light, like the light from the sun or light from a bulb, moves away from its source 【C11】______ all directions, so its strength is very spread out. The light from a laser, moving in only one direction and 【C12】______ in a narrow beam, is much stronger. Laser light is created by a 【C13】______ called stimulated emission. In this process, the atoms of a certain substance, such as a crystal or a gas, are excited 【C14】______ that they produce coherent light. A person working with a laser can aim this coherent light, 【C15】______ a laser beam, in any direction.
     As soon as the laser was developed, scientists began thinking of practical applications 【C16】______ it. One of the earliest uses was to make extremely precise measurements of distance and speed. 【C17】______ , the distance to the moon was measured to within a foot, and the speed of light was measured to 【C18】______ a thousandth of a mile per second. As time 【C19】______ , many more applications for the laser were 【C20】______ .
【C13】
选项 A、process
B、way
C、period
D、device
答案A
解析 此题考查名词的用法。看到该句中的同位语stimulated emission，就可以得出结论：激光是一个“过程"(process)，而不是“方法”(way)、“时间段”(period)或者“装置/机制”(device)。故A项符合题意。
转载请注明原文地址:https://www.kaotiyun.com/show/FZ9K777K
0

专业英语四级

相关试题推荐
随机试题
最新回复(0)