Seeing in stereo means seeing with two eyes working together，which is called stereoscopic sight．This allows you to view the world in three dimensions，or 3-D．Seeing depth helps you to judge the distance between you and the objects you see and to adjust to the changing angle at which you see something as you move closer to or farther away from it．If images are coming from only one eye, however，only two of these dimensions-height and width-can be perceived．A world seen with one eye is thus two-dimensional，as in a photograph．

　　Now consider why your two eyes are on the front of your face．Think of other animals with this same arrangement．They are all animals that hunt，like lions and wolves．Their eyes face directly in front of them．This provides a field of sight about 180 degrees wide，which is called binocular sight．On the other hand，animals that are hunted have eyes on the sides of the head，which provides nearly 360-degree field of sight．In order to stay alive，they need to see things coming from the sides and from behind．However，without stereoscopic sight，they have difficulty determining how far a danger is．

　　With sight both stereoscopic and binocular，humans share with animal hunters the ability to

　　see from side to side and to accurately determine the distance．If you think it would be great to

　　have another type of sight，perhaps with hundreds of tiny eyes like many insects do，think again! Each tiny insect eye sees only a tiny part．Besides，what if you needed glasses? Be glad for the

【江苏省扬州中学2015届高三上学期质量检测（12月）试卷 英语 Word版含答案】相关文章：

★ 河南省濮阳县第一中学2015届高三上学期期中考试英语试卷

★ 重庆复旦中学2014-2015学年高二上学期期中考试试卷 英语 Word版含答案

★ 湖南省湘中名校2015届高三11月联考英语试卷 Word版含答案

★ 福建省龙海一中2015届高三上学期第二次月考试卷 英语

★ 福建省闽清高级中学等四校2014-2015高二上学期期中联考英语试卷 Word版含答案

★ 江苏省东台市三仓中学2015届高三12月月考英语试卷

★ 四川省南充市阆南西三校2015届高三9月联考英语试卷 Word版含答案

★ 重庆市巴蜀中学2015届高三12月月考英语试卷

★ 浙江省杭州二中2014-2015学年高一上学期期中考试英语 Word版含答案

★ 福建省莆田八中2015届高三上学期第二次月考英语试卷 Word版含答案