《专业英语小论文》doc版.doc

Summary of key termsDiffraction the bending of light around an obstacle or through a narrow slit in such a way that fringes of light and or colored bands are polarized.Polarization the alignment of the electric vectors that make up electromagnetic radiation. Such waves of aligned vibrations are said to be polarized.Hologram A two-dimensional microscopic diffraction pattern that shoes three-dimensional optical images.Reading Materials:Why the Sky Is BlueIf a beam of a particular frequency of sound is directed to a tuning fork of similar frequency, the tuning forking will be set into vibration and will effectively redirect the beam in many directions. The tuning fork will be set into vibration and will effectively redirect the beam in many directions. The tuning fork scatters the sound. A similar process occurs with the scattering of light from atoms and particles that are far apart from one another, as in atmosphere.We know that atoms behave like tiny optical tuning forks and re-emit light that shine on them. Very tiny particles do the same. The tinier the particle, the higher the frequency of light it will scatter. This is similar to the way small bells ring with higher notes than larger bells, The nitrogen and oxygen molecules and the tiny particles that make up the atmosphere are like tiny bells that “ring” with high frequencies when energized by sunlight. Like sound from the bells, the re-emitted is sent in all directions. It is scattered.Most of the ultraviolet light from the sun is absorbed by a thin protective layer of ozone gas in the upper atmosphere. The remaining ultraviolet sunlight that passes through the atmosphere is scattered by atmospheric particles and molecules. Of the visible frequencies, violet is scattered the most, followed by blue, green, yellow, orange, and red, in that order. Red is scattered only a tenth as much as violet. Although violet light is scattered more than blue, our eyes are not very sensitive to violet light. The lesser amount of blue predominates in our vision, so we see a blue!The blue of the sky varies in different conditions. A principal factor is the water vapor content of the atmosphere. On clear dry days the sky is a much deeper blue than on clear days with high humidity. Places where the upper air is exceptionally dry, such as Italy and Greece, have beautifully blue skies that have inspired painters for centuries. Where there are a lot of particles of dust and other particles larger than oxygen and nitrogen molecules, the particles have been washed away, the sky becomes a deeper blue.The grayish haze in the skies of large cities is the result of particles emitted by internal combustion engines (cars, trucks, and industrial plants). Even when idling, a typical automobile engine emits more than 100 billion particles per second. Most are invisible and provide a framework to which other particles adhere. These are the primary scatterers of lower frequency light. For the larger of these particles, absorption rather than scattering takes place and a brownish haze is produced. Yuk!Why Cloud Are WhiteClusters of water molecules in a variety of sizes make up clouds. The different size clusters result in a variety of scattered frequencies: the tiniest, blue, slightly larger clusters, say, green; and still larger clusters, red. The overall result is a while cloud. Electrons close to one anther in a cluster vibrate together and in step. Which results in a greater intensity of scattered light than from the same number of electrons vibrating separately. Hence, clouds are bright!Absorption occurs for larger droplets. And the scattered intensity is less. The clouds are darker. Further increase in the size of the drops causes them to fall to earth, and we have rain!The next time you find yourself admiring a crisp blue sky, or delighting in the shapes of bright clouds, or watching a beautiful sunset, think about all those ultra-tiny optical tuning forks vibrating away youll appreciate these everyday wonder of nature even more!该部分来自专业英语课本Pg171Pg173译文如下：关键术语的总结衍射 光线通过光边或彩色带极化的方式弯曲绕过障碍物或者一个障碍物极化 电子线路的集合导致电磁辐射，这种波的定向振动称为极化。（激光）全息图 一个二维的显微镜衍射模型，表示三维光学图像。阅读材料：为什么天空是蓝色的？如果一束特定频率的声音指向一个类似频率的音叉，调谐分叉将被设置成调谐振动，并将在许多方向对光束有效地重新定向。类似音叉散射声音的过程也会伴随着光从原子或者像在大气中一样孤立的微粒子的散射产生。我们知道，原子表现的很像微小的光学音叉并且会重新放出光照亮自身。非常微小的颗粒也会发生这种现象。粒子越小，由它散射的光的频率越高。这类似于小铃铛发出的声音比大铃铛的要大。氮气、氧气和微小粒子组成的氛围就像微小的铃铛，就像被阳光激励后具有高频率的“铃”。跟钟发出的声音一样，重新发出的光射向各个方向。它是分散的。 来自太阳的紫外线大部分被大气层上部薄薄的臭氧气体保护层所吸收。剩下的辐射紫外线在穿过大气层时被常压下的分子和粒子所散射。就散射光的多少来说，按这个顺序排列：紫色最多，其次是蓝色、绿色、黄色、橙色和红色。散射而来的红光中最多只有十分之一是紫罗兰。虽然散射来的紫光比红光要多，但是我们的眼睛对紫光不是很敏感。因此较小数量的蓝光占据了优势，我们也就看到了一片蓝天！蓝色的天空在不同的条件下会发生变化。大气中水汽的含量是一个主要因素。相比晴朗但湿度比较大的时候，晴朗干燥的时候天空会更蓝一些。气层较高的地方非常干燥，例如意大利和希腊，他们拥有的漂亮的蓝色天空让画家们兴奋不已了好几个世纪。这儿的粒子尘埃以及比氧分子、氮分子大的粒子都被风吹走了，因此天空变得更加的蓝。大城市浅灰色的阴霭的天空是内燃机（汽车、卡车和工业厂房）发出的粒子造成的结果。甚至于在空转的时候，一台常见的汽车发动机会在一秒钟排放出大约1000亿个粒子。这大多数是无形的，并且会给其他粒子的粘附提供一个框架。这是频率较低的光的主要散射。对于那些较大的粒子，是吸收而不是散射导致一种褐色的阴霾的产生。哈哈!为什么云朵是白色的？各种大小的水分子团簇组成了云朵。结果大小不同的团簇导致了散射