题目内容
如图所示,用频率为 v的单色光垂直照射双缝,在光屏上的P点出现第3级暗条纹.已知光速为c ,则P点到双缝的距离之差r2﹣r1 为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241333555682413.png)
A
B
C
D ![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133355943475.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241333555682413.png)
A
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133355740435.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133355771494.png)
C
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133355818428.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133355943475.png)
D
由双缝干涉中出现暗条纹,P点到双缝的距离之差r2﹣r1满足半波长的奇数倍,r2﹣r1=(2n+1)
(n=0、1、2、3、……),因在光屏上的P点出现第3级暗条纹.所以n=2,
,得r2﹣r1=(2
+1)
=
,D正确。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133355990424.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133356036507.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133356068329.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133356114428.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133355943475.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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