Do you know when and where to look for rainbows? We hardly ever see them because they need two things together—sunlight (sunshine) and rain. We often can’t tell the color of sunlight with our eyes, but it has all the colors of a rainbow.
A rainbow appears (出现) when raindrops take these colors apart (分离). All these colors move fast at the same speed in the air: 671 million miles an hour. But when sunlight passes through water, it slows down. Some colors go through water faster than others. Red light goes first through water. Orange is almost as fast. Then comes yellow, green and blue. Purple light goes the last. As light meets water, it refracts (折射) and different speed makes different refraction. We can see a rainbow because sunlight makes some changes between the air and water.
A rainbow appears across from the sun. And when you see a rainbow, you can forecast (预测) the weather. If a rainbow appears in the morning, then the sun is in the east or southeast. So the rainbow is in the west or northwest. And weather usually moves from west to east. So maybe the rain is coming in your way. Things are different if you see a rainbow in the afternoon.
根据短文内容选择最佳答案。
【小题1】When can we see a rainbow?
| A．On sunny and rainy days. | B．On cloudy days. | C．On snowy days. |
【小题2】What does the underlined word “
speed” mean in Paragraph 2?
【小题3】What’s the main idea of Paragraph 2?
| A．When to look for a rainbow. |
| B．Where to look for a rainbow. |
| C．What makes a rainbow. |
【小题4】We can learn from the passage EXCEPT (除了) _________.
| A．a rainbow appears across from the sun |
| B．you can see red, orange, yellow, green, blue and purple in a rainbow |
| C．you can look for a second rainbow outside the first one |
【小题5】According to Paragraph 3, we can inter (推断) that ________.
| A．the sun and the weather move in the same way |
| B．the weather will be good if you see a rainbow in the afternoon |
| C．you can see a rainbow if you look at the sun |
