Vision
Human vision like that of other primates has evolved in an arboreal environment. In the dense complex world of a tropical forest, it is more important to see well than to develop an acute sense of smell. In the course of evolution members of the primate line have acquired large eyes while the snout has shrunk to give the eye an unimpeded view. 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 eyes however 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 which has receptors tuned into wavelengths longer than 0.7 micron. The world would look eerily different if human eyes were sensitive to infrared radiation. Then instead of the darkness of night, we would be able to move easily in a strange shadowless world where objects glowed with varying degrees of intensity. But human eyes excel in other ways. They are in fact remarkably discerning in color gradation. The color sensitivity of normal human vision is rarely surpassed even by sophisticated technical devices.
肚脐眼不能随便乱抠,真相原来是这样!
国际英语资讯:Richard H. Thaler wins 2017 Nobel Prize in Economics
十年一剑! 外教社汉英对照版四大名著出齐!
国内英语资讯:CPC discipline watchdog holds key plenum, approves work report
国际英语资讯:8.2-magnitude earthquake in Mexico has caused over 7,000 aftershocks
国际英语资讯:Zuma has no personal preferences in appointment of SABC Board: Presidency
张培基英译散文赏析之《无题》
英语语法测试 - 条件句的用法
国际英语资讯:Turkey wont ask U.S. for permission to detain suspects: PM
盘点好莱坞息影明星(组图)
Have a go 除了“试一试”以外还有什么意思?
国际英语资讯:Zuma reaffirms commitment to establishment of free trade area in Africa
国际英语资讯:May says Britain prepared to leave EU with no deal
穿鞋不穿袜 会得“香港脚”
体坛英语资讯:Egypt qualifies for 2018 World Cup after 2-1 win over Congo
印度小哥发明“电击鞋” 可以电击色狼并报警
国内英语资讯:China Focus: Xis inspection tours across China as top Party leader
鹿晗与关晓彤公开承认恋情
在这5个行业工作能毁了你的健康
国内英语资讯:Xi urges solid efforts to win battle against poverty