题目内容
(9分)如图在竖直放置的铅屏A的右表面上贴着能放射电子的仪器P,放射源放出的电子速度大小均为v0=1.0×107m/s,各个方向均有。足够大的荧光屏M与铅屏A平行放置,相距d=2.0×10-2m,其间有水平向左的匀强电场,电场强度大小E=2.5×104N/C。已知电子电量e=1.6×10-19C,电子质量m=9.0×10-31kg,不计电子重力。求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250025062433990.jpg)
(1)电子到达荧光屏M上的动能
(2)荧光屏上的发光面积(结果保留3位有效数字)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250025062433990.jpg)
(1)电子到达荧光屏M上的动能
(2)荧光屏上的发光面积(结果保留3位有效数字)
(1)
(2) ![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002506274799.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002506258805.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002506274799.png)
试题分析:(1)由动能定理:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002506289982.png)
得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002506258805.png)
(2) 电子各个方向均有,其中和铅屏A平行的电子在纵向偏移距离最大
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002506336853.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002506352488.png)
解得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002506367618.png)
在荧光屏上观察到的范围是半径为r的圆,
面积
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002506383534.png)
代入数值得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002506274799.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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