如图甲所示，在杨氏双缝干涉实验中，激光的波长为5.30×10-7m，屏上P点距双缝s1和s2的路程差为7.95×10-7m．则在这里出现的应是______（选填“明条纹”或“暗条纹”）．现改用波长为6.30×10-7m的激光进行上述实验，保持其他条件不变，则屏上的条纹间距将______（选填“变宽”、“变窄”、或“不变”．
屏上P点距双缝s1和s2的路程差为7.95×10-7m，则n=
=△s λ 2
=3，为奇数，在P点出现暗条纹．7.95×10-7 5.30×10-7 2
根据△x=
λ知，波长变大，则条纹间距变宽．L d
故答案为：暗条纹，变宽．
| 阅读下列短文，根据短文中的信息完成文后表格。 | |||||||||||||||||
| The world is divided into(被分为) two important parts. One half of the world is rich and the other half is poor. In the poor part, a lot of people never get enough to eat. In the rich part, a lot of people eat too much. In one part, children are hungry and in the other, a lot of people are fatter and fatter and have to go on diets or do some exercise to lose weight. For example, a dog or a cat in North America eats better than a child in the poorer countries. The poor countries have some difficult problems. Sometimes the land is too poor to grow anything on. The land can get better, but people have to do a lot of things first. More experts (专家) should go there to teach people how to enrich their land and how to find water. But rich countries have problems, too. They are not always pleasant places to live in. Sometimes the air is too dirty to breathe (呼吸) and the rivers are too dirty to swim in or to take water. The roads and the streets are full of people and buses. Cars usually move very slowly. Noise is terrible. A lot of people do not have houses to live in. People must do something about these problems. We should do something to make the air and the rivers clean and build more houses. But it will take a long time. | |||||||||||||||||
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