You stare at waterfall for a minute or two, and then shift your gaze to its surroundings. What you now see appears to drift upward.
These optical illusions occur because the brain is constantly matching its model of reality to signals from the bodys sensors and interpreting what must be happeningthat your brain must have moved, not the other; that downward motions is now normal, so a change from it must now be perceived as upward motion.
The sensors that make this magic are of two kinds. Each eye contains about 120 million rods, which provide somewhat blurry black and white vision. These are the windows of night vision; once adapted to the dark, they can detect a candle burning ten miles away.
Color vision in each eye comes from six to seven million structures called cones. Under ideal conditions, every cone can see the entire rainbow spectrum of visible colors, but one type of cone is most sensitive to red, another to green, a third to blue.
Rods and cones send their messages pulsing an average 20 to 25 times per second along the optic nerve. We see an image for a fraction of a second longer than it actually appears. In movies, reels of still photographs are projected onto screens at 24 frames per second, tricking our eyes into seeing a continuous moving picture.
Like apparent motion, color vision is also subject to unusual effects. When day gives way to night, twilight brings what the poet T.S. Eliot called the violet hour. A light levels fall, the rods become progressively less responsive. Rods are most sensitive to the shorter wavelengths of blue and green, and they impart a strange vividness to the gardens blue flowers.
However, look at a white shirt during the reddish light of sunset, and youll still see it in its true colorwhite, not red. Our eyes are constantly comparing an object against its surroundings. They therefore observe the effect of a shift in the color of illuminating on both, and adjust accordingly.
The eyes can distinguish several million graduations of light and shade of color. Each waking second they flash tens of millions of pieces of information to the brain, which weaves them incessantly into a picture of the world around us.
Yet all this is done at the back of each eye by a fabric of sensors, called the retina, about as wide and as thick as a postage stamp. As the Renaissance inventor and artist Leonardo da Vinci wrote in wonder, Who would believe that so small a space could contain the images of all the universe?
1.Visual illusions often take place when the image of reality is ___.
A.matched to six to seven million structures called cones.
B.confused in the bodys sensors of both rods and cones.
C.interpreted in the brain as what must be the case.
D.signaled by about 120 million rods in the eye.
2.The visual sensor that is capable of distinguishing shades of color is called ___.
A.cones
B.color vision
C.rods
D.spectrum
3.The retina send pulses to the brain ___.
A.in short wavelengths
B.as color pictures
C.by a ganglion cell
D.along the optic nerve.
4.Twenty-four still photographs are made into a continuous moving picture just because ___.
A.the image we see usually stays longer than it actually appears.
B.we see an object in comparison with its surroundings.
C.the eyes catch million pieces of information continuously.
D.rods and cones send messages 20 to 25 times a second.
5.The authors purpose in writing the passage lies in ___.
A.showing that we sometimes are deceived by our own eyes.
B.informing us about the different functions of the eye organs.
C.regretting that we are too slow in the study of eyes.
D.marveling at the great work done by the retina.
参考答案:
CADAB
上一篇: 英语六级阅读练习题(5)
下一篇: 英语六级阅读复习之精选练习题(5)
2017届高考英语一轮总复习精选测试题北师大版必修五Unit 13 B卷
2017届高考英语一轮总复习精选测试题北师大版必修三Unit 8 A卷
高考英语复习完形填空:专题训练16
2017届高考英语一轮总复习精选测试题北师大版必修四Unit 11 A卷
高考英语复习完形填空:专题训练4七大实用解题技巧(湖南专用)
高考英语一轮复习 高考语法通关12(新人教版)(课件)
斑马为何要过马路?在美国和英国有关驾驶的语言
高考英语一轮复习 高考语法通关4(新人教版)(课件)
2017届高考英语一轮总复习精选测试题北师大版必修五Unit 14 A卷
2017届高考英语一轮总复习精选测试题北师大版必修二Unit 5 A卷