您现在的位置: Language Tips> Easy English> Odd Question  
   
 





 
 
彩虹是怎么形成的?
[ 2006-11-24 11:10 ]

雨过天晴,天边时常会出现一道彩虹,给人带来无限的遐想。有人说,彩虹是人间通往天堂的路,有人说,彩虹是女娲补天时留下的彩石。彩虹到底是怎么形成的呢?就让下面这篇文章来为你揭开谜底吧!

彩虹是怎么形成的?The rainbow's appearance is caused bydispersionof sunlight as it is refracted by (approximatelyspherical) raindrops. The light is first refracted as it enters the surface of the raindrop, reflected off the back of the drop, and again refracted as it leaves the drop. The overall effect is that the incoming light is reflected back over a wide range of angles, with the most intense light at an angle of about 40°-42°. This angle is independent of the size of the drop, but does depend on its refractive index. As seawater has a higher refractive index than rain water, theradiusof a rainbow in a sea spray is smaller than that of a true rainbow. This is visible to the naked eye by a misalignment of these bows.

Since the water is dispersive, the amount that the sunlight is bent depends upon the wavelength, and hence color, of the light's constituent parts. Blue light is refracted at a greater angle than red light, but because the area of the back of the droplet has a focal point inside the droplet, the spectrum crosses itself, and therefore the red light appears higher in the sky, and forms the outer color of the rainbow. Contrary to popular belief, the light at the back of the raindrop does not undergo total internal reflection; however, light that emerges from the back of the raindrop does not create a rainbow between the observer and the sun. The spectra emitted from the back of the raindrop do not have a maximum of intensity, as the other visible rainbows do, and thus the colors blend together and do not form a rainbow.

A rainbow does not actually exist at a location in the sky, but rather is an optical phenomenon whose apparent position depends on the observer's location. All raindrops refract and reflect the sunlight in the same way, but only the light from some raindrops reaches the observer's eye. These raindrops are perceived to constitute the rainbow by that observer. The position of a rainbow in the sky is always in the opposite direction of the Sun with respect to the observer, and the interior is always slightly brighter than the exterior. The bow is centered on the shadow of the observer's head, or more exactly at the antisolar point (which is below the horizon during the daytime), appearing at an angle of approximately 40°-42° to the line between the observer's head and its shadow. As a result, if the sun is higher than 42°, then the rainbow is below the horizon and cannot be seen as there are usually not enough raindrops between the horizon (that is: eye height) and the ground, to contribute. One exception is when the observer is at the top of a mountain or a similar vantage point, for example an aeroplane (see below). Another exception occurs when the rainbow is produced by a garden sprinkler. Although in this case to get sufficient drops they must be very small, resulting in a quite colorless bow.

dispersion: 散射

spherical: 球面的,球状的

radius: 半径

(通讯员稿 英语点津 Annabel 编辑)

分享按钮
中国日报网英语点津版权说明:凡注明来源为“中国日报网英语点津:XXX(署名)”的原创作品,除与中国日报网签署英语点津内容授权协议的网站外,其他任何网站或单位未经允许不得非法盗链、转载和使用,违者必究。如需使用,请与010-84883631联系;凡本网注明“来源:XXX(非英语点津)”的作品,均转载自其它媒体,目的在于传播更多信息,其他媒体如需转载,请与稿件来源方联系,如产生任何问题与本网无关;本网所发布的歌曲、电影片段,版权归原作者所有,仅供学习与研究,如果侵权,请提供版权证明,以便尽快删除。
相关文章 Related Story
 
 
 
本频道最新推荐
 
翻译中的“经验法则”
明星争相打造“岁月无痕脸”
外债余额 outstanding external debt
Disrobed, famed and stranded
Black Swan《黑天鹅》精讲之一
翻吧推荐
 
论坛热贴
 
原来国家的名字如此浪漫
Funny lines about getting married
关于工资的英语词汇大全
关于职业装的英语词汇
余光中《尺素寸心》(节选)译