题目内容
将α、β、γ三种射线分别射入匀强磁场和匀强电场,图19-1-6表示射线偏转情况中正确的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241207080459038.jpg)
图19-1-6
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241207080459038.jpg)
图19-1-6
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已知α粒子带正电,β粒子带负电,γ射线不带电,根据正、负电荷在磁场中运动受洛伦兹力方向和正、负电荷在电场中受电场力方向,可知A、B、C、D四幅图中,α和β粒子的偏转方向都是正确的,但偏转的程度需进一步判断.
带电粒子在磁场中做匀速圆周运动,其半径r=
,将其数据代入,则α粒子与β粒子的半径之比为:
·
·
=
×
×
≈![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708201308.gif)
由此可见,A项正确,B项错误.
带电粒子垂直进入匀强电场,设初速度为v0,垂直电场线方向位移为x,沿电场线方向位移为y,则有:
x=v0t,y=
·
t2,消去t可得y=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708248522.gif)
对某一确定的x值,α、β粒子沿电场线偏转距离之比为
·
·
=
×
×
=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708373251.gif)
由此可见,C项错误,D项正确,故正确答案是A、D.
带电粒子在磁场中做匀速圆周运动,其半径r=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708076424.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708092510.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708092262.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708108387.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708123368.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708170344.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708186225.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708201308.gif)
由此可见,A项正确,B项错误.
带电粒子垂直进入匀强电场,设初速度为v0,垂直电场线方向位移为x,沿电场线方向位移为y,则有:
x=v0t,y=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708186225.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708232393.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708248522.gif)
对某一确定的x值,α、β粒子沿电场线偏转距离之比为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708264512.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708279403.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708108387.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708326221.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708342364.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708357493.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120708373251.gif)
由此可见,C项错误,D项正确,故正确答案是A、D.
![](http://thumb2018.1010pic.com/images/loading.gif)
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