题目内容
(6分)如图所示是透明圆柱形介质的横截面,BC为圆的直径。一束单色光沿AB方向入射,
ABC=120o。光自B点进入介质内只经过一次折射后从介质中射出,出射光线平行于BC。
①求介质的折射率;
②若改变
ABC的大小,则从B点射入介质中的单色光能否在介质的内表面发生全反射?答: (填“能”或“不能”)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250042226932871.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004222630263.png)
①求介质的折射率;
②若改变
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004222630263.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250042226932871.jpg)
①
;②不能;
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004222708346.png)
试题分析:
①入射角i=180°-∠ABC=60°;设光线从圆柱形介质中的出射点为D,出射光线DE
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250042227245817.png)
由对称性和光路可逆原理知:α=60°
因DE∥BC,故β=60°,∴∠BOD=120°
∴光线在B点的折射角:r=30°
折射率:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250042227551072.png)
②不能
![](http://thumb2018.1010pic.com/images/loading.gif)
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