题目内容
对光学仪器定标时,需要确定两条平行光线的精确间距x.可以用如下办法:先使两条光线垂直且对称地射到一根圆柱形的玻璃棒上,如图所示,棒的半径为R,折射率n=1.60,然后调节两条光线间的距离,直到它们正好聚焦在玻璃棒圆周上对面的一点.试求x.![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241147559996181.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241147559996181.jpg)
1.92R
本题考查光的折射.
设入射角为
,折射角为
,由几何关系知
=2![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114756030218.gif)
则n=
=2cos
=1.6
解得cos
=0.8
sin
=
=0.6
sin
=nsin
=1.6×0.6=0.96
则x=2Rsin
=1.92R.
设入射角为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114756014217.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114756030218.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114756014217.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114756030218.gif)
则n=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114756248773.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114756030218.gif)
解得cos
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114756030218.gif)
sin
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114756030218.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114756311390.gif)
sin
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114756014217.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114756030218.gif)
则x=2Rsin
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114756014217.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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