P、Q是一列简谐横波中的质点，相距30m，各自的振动图象如图所示._爱下问搜题

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问题填空题

P、Q是一列简谐横波中的质点，相距30m，各自的振动图象如图所示.

(1)此列波的频率f＝________Hz.

(2)如果P比Q离波源近，且P与Q间距离小于1个波长，那么波长λ＝________m，波速v＝________m/s.

答案

(1)0.25　(2)40　10

(1)该波的周期为４ｓ，频率（2）P的振动传播到Q点需要，两点距离为四分之三个波长，所以波长为40m，波速

完形填空

When I was thirteen, my family moved from Boston to Tucson, Arizona. __36__the move, my father __37__us in the living-room on a freezing January night. My sisters and I sat around the fire, not __38__ that the universe would suddenly change its course. “In May, we′re__39__ to Arizona.”
The words, so small, didn't seem__40__enough to hold my new life. But the world changed and I awoke on a tram moving across the country.1 watched the __41__change from green trees to flat dusty plains to high mountains as I saw strange new plants that __42__ mysteries yet to come. Finally, we arrived and __43__ into our new home.
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“Are you new to this neighborhood?” I explained that I was, __48__,new to the entire state．
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单项选择题

下列选项中，不应缴纳增值税的是( )。

A．销售甲烷的收入

B．出售自产的家具的收入

C．加工金项链一条的收入

D．销售房屋一套的收入