passage51

51. The Colorful World The world around us is full of colors: the grass is green, the sky is blue. What a pity it will be if people can not see all the colors. But there are people who are blind to certain colors. Human color blindness is a strange thing to explain In a single eye there are millions of very small things called “cones(锥形物)”. They help us to see in bright light and to tell the difference between colors There are also millions of “rods(视网膜杆)”but they are used for seeing when it is nearly dark. They show us shape but not the color. Some birds and animals' eyes have few or no cones, so they cannot see colors. cats and dogs cannot see colors as well as we can Some insects(昆虫) can even see X-rays. Scientists know that there are other colors around us which insects can see but which we cannot see. Human beings have favorite colors. Blue is often popular because it is the color of the cool sky and sea Green is the color which makes us think of grass, field and forest. Yellow is the color of the sun. On the other hand, red is the color of blood and fire. It makes some people think of accidents, danger and blood. Black is the color of the night. In the dark we cannot see what is around us, so we are sometimes afraid of the unknown and do not like black as a color. 51．多彩的世界 我们周围的世界充满(be full of)色彩：草(grass)是绿色的，天空是蓝色的。如果人看不到所有这些颜色，那将是多么遗憾的事呀！但有些人对某些颜色的确是看不见的(blind)。 人类的色盲很难解释。在一只眼睛(a single eye)里有几百万(millions of)叫做“视锥”的微小物质。它们帮助我们在亮光(bright light)下看清并辨别颜色的差异(tell the difference between colors)。单眼中也有几百万“视网膜杆”，但它们是用来(be used for)在天色几乎(nearly)黑下来时看清东西的，它们为我们显示形状(shape)而非颜色。 一些鸟和动物的眼睛有很少(few)或没有视锥，所以它们看不到颜色。猫和狗不能和我们一样看清颜色。 一些昆虫甚至可以看到X射线(X-ray)。科学家们知道，我们周围有些其他颜色昆虫可以看到而我们却无法看到。 人类有最偏爱的颜色。蓝色常受欢迎是因为它是凉爽的天空和海洋的颜色。绿色是让我们想起草地、骤野和森林的颜色，黄色是太阳(sun)色。另一方面，红色是血(blood)与火(fire)的颜色，使一些人想起事故、危险和流血。黑色是夜的颜色．在黑暗中(in the dark)，我们看不到周围的一切，所以我们有时害怕未知的(unknown)事物，不喜欢黑色。