振幅不同，波速相同的两列波相向传播，它们的周期都为T，相遇的过程如图所示，从这个过程中能总结出波的叠加的规律是：
（1）______；
（2）______．
当左列波和右列波相遇时，叠加时的振动方向相同的，则相互加强；当振动方向相反时，则相互抵消．
当两列波的波峰或波谷相遇时，则振幅变为两者之和，
当相遇后，波相互不影响，各自向前传播．
故答案为：（1）当波相遇时，振动方向相同的部分振动加强，振动方向相反的部分振动减弱
（2）波相互穿过，互不干扰
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| It was the golden season . I could see the yellow leaves 1 on the cool 2 . In such a season, I liked walking alone in the leaves, listening to the sound of them. Autumn is a 3 season and life is uninteresting. The free days always get me 4 . But one day, the sound of a violin 5 into my ears like a stream flowing in the mountains. I was so surprised that I jumped to see what it was. A young girl, standing in the wind, was 6 in playing her violin. I had 7 seen her before. The music was so attractive(有吸引力) that I listened quietly. Lost in the music, I didn't realize that I had been 8 there for so long but my 9 did not seem to disturb(打扰) her. Leaves were still falling. Every day she played the violin in the corner of the building 10 I went downstairs to watch her performance. I was the only audience. The autumn seemed no longer lonely and life became 11 . 12 we didn't know each other, I thought we were already good friends. I believed she also liked me . Autumn was nearly over. One day, when I was listening devotedly, the sound suddenly stopped. To my 13,the girl came over to me. " You must like violin," she said. "Yes. And you play very well. Why did you stop?" I asked. Suddenly, a 14 expression appeared on her face and I could feel something unusual. "I came here to see my grandmother, but now I must leave. I once played very badly. It was your listening every day that 15 me. " she said. "In fact, it was your playing 16 gave me a meaningful autumn." I answered. "Let us be friends." The girl smiled and I smiled. I never heard her play again in my life. I no longer went downstairs to listen like before. Only thick leaves were left behind. But I will always remember the fine figure of the girl. She is like a 17 ; so short, so bright, like a shooting star giving off so much light that it makes the autumn beautiful. There are many kinds of friends. Some are always 18 you, but don't understand you. Some say only a few words to you, but are close to you. Many people will step in your life, but only 19 friends leave footprints(脚印). I shall always recall the autumn and the girl with the 20 . She will always bring back the friendship between us. I know she will always be my best friend. | ||||
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