题目内容
下图所示的圆形区域内存在着匀强磁场,磁感应强度大小为B,方向垂直纸面向里,该区域的半径为R.一质量为m、带电量为q的带电粒子,以速率v0(
)从圆周上的A点射入,v0的方向限定在纸面内.求粒子沿什么方向入射,能有最大偏转角?最大偏转角是多大?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241157275371537.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241157273811102.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241157275371537.gif)
当粒子从过A点的直径的另一端点C点射出时,偏转角才最大,
2θ=" "![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241157275841167.gif)
2θ=" "
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241157275841167.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241157275991875.gif)
粒子的速度v0值大小一定,垂直进入磁场后做圆周运动的轨道半径r=mv0/Bq(r>R).在r值一定的条件下,粒子在磁场中运动的轨迹越长,则偏转角度越大,因此,只有当粒子从过A点的直径的另一端点C点射出时,偏转角才最大,如图所示.设入射方向与AO间夹角为θ,由几何关系
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241157276151185.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241157275841167.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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