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  3. The word laser was coined as an acronym for Light Amplification by the Stimul

The word laser was coined as an acronym for Light Amplification by the Stimul

游客2024-10-30  9
问题    The word laser was coined as an acronym for Light Amplification by the Stimulated Emission of Radiation. Ordinary light, from the Sun or a light bulb, is emitted spontaneously, when atoms or molecules get rid of excess energy by them-selves, without any outside intervention. Stimulated emission is different because it occurs when an atom or molecule holding onto excess energy has been stimulated to emit it as light.
   Albert Einstein was the first to suggest the existence of stimulated emission in a paper published in 1917. However, for many years physicists thought that atoms and molecules always were much more likely to emit light spontaneously and that stimulated emission thus always would be much weaker. It was not until after the Second World War that physicists began trying to make stimulated emission dominate. They sought ways by which one atom or molecule could stimulate many others to emit light, amplifying it to much higher powers.
   The first to succeed was Charles H. Townes, then at Columbia University in New York. Instead of working with light, however, he worked with microwaves, which have a much longer wavelength, and built a device he called a "maser," for Microwave Amplification by the Stimulated Emission of Radiation. Although he thought of the key idea in 1951, the first maser was not completed until a couple of years later. Before long, many other physicists were building masers and trying to discover how to produce stimulated mission at even shorter wavelengths.
   The key concepts emerged about 1957. Townes and Arthur Schawlow, then at Bell Telephone Laboratories, wrote a long paper outlining the conditions needed to amplify stimulated emission of visible light waves. At about the same time, similar ideas crystallized in the mind of Gordon Gould, then a 37-year-old graduate student at Columbia, who wrote them down in a series of notebooks. Townes and Schawlow published their ideas in a scientific journal, Physical Review Letters, but Gould filed a patent application. Three decades later, people still argue about who deserves the credit for the concept of the laser. [br] Why was Towne’s early work with stimulated emission done with microwaves?
选项 A、He was not concerned with light amplification.
B、It was easier to work with longer wavelengths.
C、His partner Schawlow had already begun work on the laser.
D、The laser had already been developed.
答案 B
解析 为什么汤尼斯早期的刺激性放射工作是用微波来进行的?A他对光的扩散不感兴趣；B和更长的波长一起使用更方便；C他的伙伴 Schawlow已经开始对激光的研究；D激光已经被开发。第三段第一，二句话表明：最初的成功人物是查尔斯H-汤尼斯，他在纽约的哥伦比亚大学(美)工作。没有用光来工作，他利用微波，因为它有更长的波长。他还建造叫做微波激射器的装置，为辐射刺激性放射的微波扩大。故应选B。
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