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 that 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 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.
2017届高考英语一轮复习指导课件:必修3 unit 4(新人教版)
2017届高考英语一轮复习指导课件:必修3 unit 1(新人教版)
2017届高考英语一轮复习技能提升练:选修7 Unit 5《Travelling abroad》(新人教版含解析)
2017届高考英语一轮循环写作周周练:第8周 灵活好用的名词性从句(新人教版含解析)
2017届高考英语一轮循环写作周周练:第1周 各司其职的8大句子成分(新人教版含解析)
2017届高考英语一轮复习指导课件:选修7 unit 4(新人教版)
2017届高考英语一轮复习指导课件:必修3 unit 3(新人教版)
2017届高考英语一轮复习指导课件:必修4 unit 1(新人教版)
2017届高考英语一轮复习指导课件:必修3 unit 5(新人教版)
2017届高考英语一轮循环写作周周练:第6周 富有文采的状语从句(新人教版含解析)
2017届高考英语一轮复习技能提升练:选修7 Unit 3《Under the sea》(新人教版含解析)
2017届高考英语一轮复习指导课件:选修6 unit 4(新人教版)
2017届高考英语一轮循环写作周周练:第11周 彰显水平的强调句型、倒装句型和There be句型(新人教版含解析)
2017届高考英语一轮复习指导课件:必修3 unit 2(新人教版)
2017届高考英语一轮循环写作周周练:第7周 吸引眼球的定语从句(新人教版含解析)
2017届高考英语一轮复习指导课件:必修5 unit 5(新人教版)
2017届高考英语一轮复习技能提升练:选修8 Unit 3《Inventors and inventions》(新人教版含解析)
2017届高考英语一轮复习指导课件:选修9 unit 3(新人教版)
2017届高考英语一轮复习指导课件:选修7 unit 1(新人教版)
2017届高考英语一轮复习指导课件:选修7 unit 2(新人教版)
2017届高考英语一轮复习技能提升练:选修8 Unit 1《A land of diversity》(新人教版含解析)
2017届高考英语一轮循环写作周周练:第10周 言简意明的非谓语动词(新人教版含解析)
2017届高考英语一轮复习指导课件:必修5 unit 1(新人教版)
2017届高考英语一轮循环写作周周练:第5周 整齐和谐的并列句(新人教版含解析)
2017届高考英语一轮复习指导课件:选修6 unit 5(新人教版)
2017届高考英语一轮复习指导课件:必修4 unit 2(新人教版)
2017届高考英语一轮循环写作周周练:第9周 避免头重脚轻的it句式(新人教版含解析)
2017届高考英语一轮复习指导课件:选修7 unit 5(新人教版)
2017届高考英语一轮复习指导课件:选修9 unit 4(新人教版)
2017届高考英语一轮复习指导课件:必修4 unit 5(新人教版)
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