美国英语听力80篇2 Lesson36

[00:06.37]Some people cannot see all colors correctly.

[00:10.92]They cannot see all the colors in a rainbow or a sunset.

[00:16.40]They cannot tell if the meat they are cooking is done or if a fruit is ready to be eaten.

[00:23.61]Poor color sight also prevents people from holding jobs such as policeman, pilot, and cook, and from serving in the military.

[00:34.59]Last year,the first eyeglasses were approved in the United States to treat people with poor color sight.

[00:43.60]They are called ColorMax glasses.

[00:46.68]However, the Food and Drug Administration warns that the new glasses do not give a person normal color vision.

[00:55.90]The glasses permit a person to better see differences in colors that used to look the same to them.

[01:02.90]About 250,000,000 people around the world have a condition limiting the colors they see.

[01:11.42]The condition commonly is known as color-blindness.

[01:16.20]Color-blindness can result from injury to the eye, medicine, or age.

[01:22.36]However, most people are born with the condition.

[01:26.44]Genetic colorblindness is caused by a defect in the retina, the inner wall of the eyeball.

[01:34.12]The retina contains cones 2 and rods, two kinds of cells that react to light.

[01:41.38]Cones permit us to see color and to see in bright light. Rods sense brightness and darkness.

[01:50.63]A normal eye has three cones. One cone 1 is sensitive to blue light, one to green light,and another to red light.

[02:01.13]Most colors are a mixture of the three colors.

[02:05.44]Usually when a person sees an object, all three cones become active.

[02:12.57]The brain then uses this information to decide the color.

[02:17.59]A normal eye can see about 200 colors.

[02:22.11]People with poor color sight have damaged or missing cones.

[02:27.44]They may see the world in as few as five colors.

[02:32.06]The most common type of color-blindness is the failure to see reds or greens.

[02:39.43]The ColorMax glasses improve color sight by changing the wavelength 3 of light entering the eye.

[02:47.78]They do so by covering the glass with a colored lens that blocks out light.

[02:55.26]For example, a red lens lets in red light but blocks out most blues 4 and greens.

[03:01.73]Green light seen through red lenses will appear darker because light from it is not reaching the eye.

[03:09.86]The glasses make colors brighter and darker so that the differences are easier to see.

[03:17.77]People say ColorMax glasses help them see an increased number of colors.