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

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

游客2023-09-13  28
问题     The word "laser" was coined as an acronym for Light Amplification by the Stimulated Emission of Radiation. Ordinary light, from the Sun of a light bulb, is emitted spontaneously, when atoms or molecules get rid of excess energy by themselves, without any outside intervention. Stimulated emission is different because it occurs when an atom of molecules 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 emission at even shorter wavelengths.
    The key concepts emerged about 1957. Townes and Arthur Schawlow, 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 Letter, but Gould fried a patent application. Three decades later, people still argue about who deserves the credit for the concept of the laser. [br] Which of the following statements best describes a laser?
选项 A、A device for stimulating atoms and molecules to emit light.
B、An atom in a high-energy state.
C、A technique for destroying atoms or molecules.
D、An instrument for measuring light waves.
答案 A
解析 事实细节题。见第一段最后一句可知，激光是在对于蕴含多余能量的原子或分子予以刺激使其发光时得到的，这正是A“一种刺激原子或分子发光的机制”这一项的意思。由此可知A为正确答案。B为“高能原子”，文章虽提到蕴含多余能量的原子，但通过原文可以判断出这并不是对laser的诠释，故排除B；C为“破坏原子或分子的技术”，文中并没有涉及这一点，所以也应排除C：D为“测试光波的仪器”，这实际上是对maser本义的解释，因此同样应排除D。
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