陳蕙雅思教材 - 雅思閱讀精選 (Vision)

Vision

Human vision like  that of other primates has evolved in  anarboreal

environment. In the densecomplex world  of a          tropical forest, it is more

important to seewell  than  to develop an acute sense of smell. In the

course of       evolution members of the primate linehave acquired large eyes

while the snout hasshrunk to give the eye an    unimpededview. Of mammals

only humans and  some primates  enjoy  color vision.  The  red flag  is  

black  to the  bull.    Horses live  in  a monochrome world. Light

visible to human eyeshowever occupies only a very narrow band in the whole

electromagnetic  spectrum. Ultraviolet  rays  are invisible  to  humans  

though  ants and honeybees are sensitive to them. Humans have no  direct  

perception  of infrared rays unlike the rattlesnake whichhas receptors

tuned into      wavelengths longer than 0.7 micron. Theworld would look  eerily

different  if human eyes were sensitive to infrared     radiation. Then instead

of  the darkness of night, we would be able tomove easily in a strange

shadowless world   where objects glowed with varying degrees ofintensity.

But human eyes excel inother ways. They are in fact remarkably discerning

in color gradation. Thecolor sensitivity of normal human vision is rarely

surpassed even by   sophisticated technical devices.

視覺

人類的視覺，和其它靈長目動物的一樣，是在叢林環境中進化出來的。  在稠密、複雜 的熱帶叢林裡，好的視覺比靈敏的嗅覺更加重要。

在進化過程中，靈長目動物的眼睛變大， 同時鼻子變小以使視野不受阻礙。  在哺乳類動物中，只有人和一些靈長目動物能夠分辨顏 色。  

紅旗在公牛看來是黑色的，馬則生活在一個單色的世界裡。  然而，人眼可見的光在整

個光譜中只占一個非常狹窄的頻段。人是看不到紫外線的，儘管螞蟻和蜜蜂可以感覺到。與 響尾蛇不同，人也不能直接感受到紅外線。  

響尾蛇的感覺器可以感受波長超過 0.7  微米的 光線。  如果人能感受到紅外線的話，這世界看上去將十分不同，而且恐怖。  到那時，將與

夜的黑暗相反，我們能輕易地在一個奇異的沒有陰影的世界裡走動。  任何物體都強弱不等 地閃著光。  然而，人眼在其它方面有優越之處。  

事實上，人眼對顏色梯度具有非凡的分辨 能力。  普通人類的視覺感受色彩的靈敏程度，甚至連精密的技術裝備都很難超越。