毕业设计定稿（论文）朱玲 - 图文(2)

湖南工业大学本科毕业论文

目 录

第1章 绪论 ·················································································· 1

1.1 光电效应的发展历史 ·························································································· 1 1.2 光电效应的应用概况 ·························································································· 4 1.3 本文的主要工作内容 ·························································································· 4

第2章 光电效应 ··········································································· 5

2.1 与光电效应相关的基础知识 ············································································ 5 2.1.1光的产生机制 ······························································································· 5 2.1.2 光的波粒二象性 ·························································································· 6 2.2 光电效应的基本概念 ························································································ 7 2.2.1外光电效应 ····································································································· 7 2.2.2内光电效应 ····································································································· 8 2.3 光电效应实验 ······································································································ 9 2.3.1 实验装置 ········································································································ 9 2.3.2 实验规律 ······································································································ 10 2.4 爱因斯坦的光量子说 ························································································· 11 2.4.1光电方程 ········································································································ 11 2.4.2光电效应的量子解释 ···················································································· 11 2.5 提高光电效应的途径 ························································································ 13

第3章 光电效应的应用 ······························································· 14

3.1 外光电效应的应用 ···························································································· 14 3.2 内光电效应的应用 ···························································································· 15 3.2.1光电导效应的应用 ······················································································· 15 3.2.2光伏特效应的应用 ······················································································· 16 3.3 光电效应的应用领域 ························································································ 17 3.3.1在工业生产中的应用 ··················································································· 17 3.3.2在农业中的应用 ··························································································· 17 3.3.3在放射医学中的应用 ··················································································· 18 3.3.4在军事中的应用 ··························································································· 19

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湖南工业大学本科毕业论文

3.3.5其它应用 ··········································································································· 20 3.4 光电效应应用前景与展望 ······················································································ 20

结论 ······························································································· 22 参考文献 ······················································································· 23 致谢 ······························································································· 24

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湖南工业大学本科毕业论文

第1章 绪论

1.1光电效应的发展历史

1885年，赫兹用如图1.1所示的装置证实了电磁波的存在。实验中电磁波发生器是在两根铜棒上各焊一个磨光的黄铜球，另一端各连接一块正方形锌板，它们共轴放置，两球间留有一空隙，它们相当于一个电容器，与感应圈两端连接，构成了LC电路，感应圈使两黄铜球聚集大量电荷，从而在空隙间产生电火花，形成高频振荡电流，辐射高频电磁波。与这个回路间隔一定距离放置一电磁波接收器，它是用一根粗铜导线弯成一开口的圆环，开口端各焊一黄铜球，之间有可作微调的空隙，这个接收器实际上也是一个LC电路．调节间隙改变接收电路的固有频率可与发射过来的电磁波产生共振，从而在接收器的空隙间观察到电火花。

图1.1 电火花实验装置

感应圈 发射

接收

利用电火花实验装置，赫兹测量了电磁波速、进行了研究电磁波的反射、聚焦、折射、衍射、干涉、偏振等各种波现象的实验，大量反复地实验不但证实了麦克斯韦电磁波理论，同时意外地发现了表明光具有粒子性的一个重要现象：当发射器间隙的火光被阻隔时，原来接收间隙的火花变暗，而用其它任何火花的光照射到接收器铜球，也能促使间隙发生电火花，进一步研究发现这一现象中直接起作用的是火光中的紫外线，当火花的光照到间隙的负极时，作用最强，这种情况下接收器间隙发生的电火花实际上是紫外线的照射使一极铜球上飞出电子到另一极铜球所形成，赫兹称之为“紫外光放电效应”，也就是光电效应。赫兹的论文《紫外光对放电的影响》发表在１８８７年《物理学年鉴》上。该论文详细地描述了他的发现。

赫兹的发现吸引了许多人去做这方面的研究工作[1]，1889年，哈耳瓦克做了一系列实验，他用碳弧照射绝缘的锌板，锌板连接到验电器上，他发现:如果锌板原来带负电，经照射会迅速失去电荷；如果锌板原来带正电，经照射仍保持不变。在碳弧前面用一块玻璃隔开，现象消失，说明起作用的确实是紫外光，从锌板放出的肯定是负电

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湖南工业大学本科毕业论文

荷。俄国的斯托列托夫（1836----1896）对光电效应也进行了研究，并取得了重要成果。他发现：为了产生光电流，光必须被电极吸收；光电流的大小与入射光的强度成正比；光电流实际上是在照射开始时立即产生，无需时间上的积累。

在光电效应的研究过程中，做出重要贡献的是德国物理学家、赫兹的助手勒纳德。他早在1889年就开始做一些简单的光电效应实验，起先他设想光电效应是阴极射线引起的，但1894年他的实验证明这一想法不符合事实。1899年，J.J.汤姆逊用磁偏切断电流的方法测定光电流的荷质比，肯定光电流与阴极射线都是同一类带电粒子组成，勒纳德随即于1900年也用磁偏转法测定光电流的荷质比得到同样的结果。其实验装置如图1.2所示，当入射光照到清洁的金属表面（阴极K）就有电子发射出来，若有些电子射到到阳极A上，外电路上就有电流通过。阳极相对于阴极的电势可正可负，以使到达阳极的电子数增加或减少。

图1.2 磁偏转法实验装置 图1.3不同强度下电流与电压的关系

图1.3表示两种强度不同的入射光照射到阴极K上，测得的电流与电压的关系曲线。当阳极A电势高于阴极K时，电子被吸引到阳极上，当电压值U足够大时，K极上所有发射出的电子全部到达阳极，因而电流达到它的最大值。勒纳德观测到此最大的饱和电流与入射光强度成正比，他并且创造了一种实验方法,用加反向电压的方法来测电子的最大速度，从而得到反向电压（又称遏止电压）与入射光光强无关，即电子离开金属极板的最大速度与光强无关。从图1.3看出，不同光强的遏止电压均为（-U0）这结论与经典理论显然相矛盾。

勒纳德用不同材料做阴极，用不同光源照射，发现都对遏止电压有影响，唯独改变光的强度对遏止电压没有影响。电子逸出金属表面的最大速度与光强无关，这就是勒纳德的新发现。。

和经典理论有抵触的实验事实还不止此，在勒纳德之前，人们已经遇到了其他的矛盾，如：1）光的频率低于某一临界值时，不论光有多强，也不会产生光电流，可

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湖南工业大学本科毕业论文

是根据经典理论，应该没有频率限制。2）光照到金属表面，光电流立即就会产生，可是根据经典理论，能量总要有一个积累过程。

本来，这些矛盾正是揭露了经典理论的不足，可是，勒纳德却煞费苦心地想出了一个补救办法，企图在不违反经典理论的前提下，对上述事实作出解释。他在1902年提出触发假说，假设在电子的发射过程中，光只起触发作用，电子原本就是以某一速度在原子内部运动，光照到原子上，只要光的频率与电子本身的振动频率一致，就发生共振，所以光只起打开闸门的作用，闸门一旦打开，电子就以其自身的速度从原子内部逸走。他认为，原子里电子的振动频率是特定的，只有频率合适的光才能起触发作用。他还建议，由此也许可以了解原子内部的结构。勒纳德的触发假说很容易被人们接受，当时颇有影响。

与勒纳德的观点不同，1905年，爱因斯坦在著名论文《关于光的产生和转化的一个试探性观点》中发展了普朗克的量子假说，提出了光量子概念，并应用到光的发射和转化上，很好地解释了光电效应等现象。

爱因斯坦在他的论文中，总结了光学发展中微粒说和波动说长期争论的历史，揭示了经典理论的困境，提出只要把光的能量看成不是连续分布，而是一份一份地集中在一起，就可以作出合理的解释。他写道：“在我看来，如果假定光的能量在空间的分布是不连续的，就可以更好地理解黑体辐射、光致发光、紫外线产生阴极射线（即光电效应），以及其它有关光的产生和转化的现象的各种观测结果。根据这一假设，从点光源发射出来的光束的能量在传播中将不是连续分布在越来越大的空间之中，而是由一个数目有限的局限于空间各点的能量子所组成。这些能量子在运动中不再分散，只能整个地被吸收或产生。”

爱因斯坦的光量子假设和光电方程完全能够解释光电效应中的各种现象，但并没有立即得到人们的承认，直到1916年，密立根的精确实验才完全证实了爱因斯坦的

光电方程。

图1.4 密立根证明光电方程的实验装置

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