用考网 > 外语类 > 英语六级 > 阅读理解 > 《英语六级阅读例句练习附详解：视力研究》正文

英语六级阅读例句练习附详解：视力研究

用考网【阅读理解】编辑：楚欣发布时间：2015-12-08 11:29:55

　　下面是学习啦小编整理的英语六级阅读例句练习附详解：视力研究，希望对大家有帮助。

　　The human criterion for perfect vision is 20/20 forreading the standard lines on a Snellen eye chartwithout a hitch. The score is determined by howwell you read lines of letters of different sizes from20 feetaway. But being able to read the bottom lineon the eye chart does not approximate perfectionas far as other species are concerned. Most birds would consider us very visuallyhandicapped. The hawk. for instance,has such sharp eyes that it can spot a dime on thesidewalk while perched on top of the Empire State Building+ It can make fine visual distinctionsbecause it is blessed with one million cones per square millimeter in its retina(视网膜). And inwater, humans are farsighted. while the kingfisher, swooping down to spear fish. can see well inboth the air and water because it is endowed with two foveae.(凹窝)-areas of the eye, consistingmostly of cones. that provide visual distinctions. One fovea permits the bird, while in theair. toscan the water below with one eye at a time. This is called monocular vision. Once it hits thewater, the other fovea joins in, allowing the kingfisher to focus both eyes, like binoculars, on itsprey at the same time. A frog's vision is distinguished by its ability to perceive things as aconstant motion picture. Known as "bug detectors", a highly developed set of cells in a frog'seyes responds mainly to movingobjects. So, it is said that a frog sitting in a field of dead bugswouldn’t see them as food and would starve.

　　The bee has a "compound" eye. which is used for navigation. It has 15,000 facets that dividewhat it sees into a pattern of dots. or mosaic. With this hind of vision, the bee sees the sunonly as a single dot, a constant point of reference. Thus. the eye is a superb navigationalinstrument that constantly measures the angle of its line of flight in relation to the sun. Abee's eye also gauges flight speed. And if that isnot enough to leave our 20/20 "perfect vision”paling into insignificance. the bee is capable of seeing something we can't-ultraviolet light.Thus,what humans consider to be "perfect vision” is in fact rather limited when we look atother species. However, there is still much to be said for the human eye. Of all the mammals,only humans and some primates can enjoy the pleasures of color vision.

　　判断人的视力是否完好的标准是看他是否在看Snellen视力表的时候能毫无障碍地达到20/20的视力。[1]测试值取决于从20英尺之外，你能看到多少行大小不一的字母。但是，即使我们能看到视力表的最底一行，和别的物种相比，那也不意味着拥有完美的视力。大多数的鸟类可能觉得我们在视力上都有缺陷。[2]例如，鹰的视力非常锐利，当它盘踞在帝国大厦的楼顶时，它能看清在人行道上的一角硬币。它有如此好的视觉分辨能力，是因为它的视网膜上每平方毫米就有100万个圆锥细胞。在水中，人类是远视的;相比之下，俯冲到水里捉鱼的翠鸟在水上和水下都能看清景物，因为它的眼睛里有两个凹窝区域，这两个凹窝主要由具有视觉分辨能力的圆锥细胞组成。[3]其中一个凹窝让飞翔在空中的翠鸟不时用一只眼瞳扫视水面的情况——这被称为单眼视觉。翠鸟一旦扎入水中，另一个凹窝也发挥功能，使它的双眼像双筒望远镜一样同时聚焦到猎物身上。青蛙的视力特点是它能感知像移动画面那样的物体。青蛙被称为“昆虫探测器”，在它的眼睛里有一组高度发达的细胞，主要能够对移动的物体产生反应。所以，据说，如果青蛙坐在一片虫子的尸体旁，它看不到那些可以作为食物的虫干，最终会被饿死。

　　蜜蜂的眼睛是复眼，用于导航。它的眼睛有15000个面，把它看到的物体分割为马赛克式的小点。[4]有了这种视觉特点，蜜蜂看到的太阳只是一个小点，一个不变的参照点。所以，它的眼睛是一个极好的导航仪器，能不断地量度飞行的线路与太阳的角度。蜜蜂的眼睛还能测量飞行的速度。如果这样还不能让我们人类20/20的完美视力显得微不足道的话，蜜蜂还能看到紫外线，这是我们人类无法看到的。因此，当我们与别的特种相比时,人类认为“完美的视力”实际上很有局限性的。然而，对于人类的眼睛还是有很多可以称赞的：在所有哺乳动物当中，只有人类和某些灵长类动物能享受分辨颜色的喜悦。

　　1. The Snellen eye chart measures one'seyesight by__________________.

　　A) the number of lines he reads

　　B) the distance he stands away from the chart

　　C) the speed at which he recognizes the letters

　　D) several integrative factors

　　2. How is hawk's eyesight better than ours?

　　A) It can identify small items more quickly than we do.

　　B) It can see ai a longer distance than we do.

　　C) It has more cones in che retina than we do.

　　D) It has bigger eyes than we do.

　　3. Monocular vision enables the kingfisher to__________________.

　　A) avoid farsightedness