题目内容
下图是光电效应实验示意图.当能量为
的光照射金属K时,产生光电流.若K的电势高于A的电势,且电势差为
,光电流刚好截止.那么当A的电势高于K的电势,且电势差也为
时,光电子到达A极的最大动能是多大?此金属的逸出功是多大?![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241351401778139.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824135139989587.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824135140036465.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824135140036465.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241351401778139.png)
K的电势高于A的电势,电场线向右,电子所受电场力向左,电子逸出后运动到A点速度刚好减小到零,由动能定理可知,最大初动能为0.9eV,由
可知逸出功为3.1eV-0.9eV=2.2eV,当A的电势高于K的电势,且电势差也为
时,由动能定理
1.8ev
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824135140223739.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824135140036465.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824135140317736.png)
本题考查光电效应原理和光电管知识,根据电子发出后减速到A速度为零,再由动能定理求解,根据光电效应公式
可求出逸出功大小
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824135140223739.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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