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爱因斯坦,1905 马红孺 上海交通大学理论物理研究所,上海市物理学会 宁夏大学物电学院 Homepage: http://hrma.physics.sjtu.edu.cn 2005 + (=) H 1L hH(=) :,XE HU 3(· :E HUAE !' '; 8GTPQPQS 8gGTPQPQPQOS (· :*ób 1879H3 14 ~ 1979H > ZL (M (· :A E ,R< H4~ F / 0, t 0, t> 0 #5 ^ E E o_ J : s2= 0 #5 ,X 5 E' #5 ,XC^ s2>光强 CU ν0 0U ν CU O 截至频率 光电效应实验规律 1, 饱和光电流强度与入射光强度成正比. 2, 对于每种金属材料,都相应的有一确定的截止 频率ν0 ,当入射光频率ν> ν0时,电子才能逸出金 属表面. 当入射光频率ν ν0时,反向遏止电压与光强无关. 0||U 3,光电效应是瞬时的.从光开始照射到光电逸出所 需时间<10-9s. ν∝ 经典理论无法解释光电效 应的实验结果 按照经典电磁理论,入射光的光强越大,光波 的电场强度的振幅也越大,作用在金属中电子上的 力也就越大,光电子逸出的能量也应该越大. 光电子的能量应该随着光强度的增加而增大,不 应该与入射光的频率有关,更不应该有什么截止频 率. 光电效应实验表明:饱和电流不仅与光强有关而且 与频率有关,光电子初动能也与频率有关.只要频率 高于红限,既使光强很弱也有光电流;频率低于红限 时,无论光强再大也没有光电流. 光电效应具有瞬时性.而经典认为光能量分布在 波面上,吸收能量要时间,即需能量的积累过程. 为了解释光电效应,爱因斯坦在能量子假说的基 础上提出光子理论,提出了光量子假设. 光量子假设光量子假设 光不仅在发射和吸收时以能量为hν的微粒 形式出现(普朗克假定),而且在空间传播时 也是如此. 频率为ν的光是由大量能量为ε=hν光子 组成的"粒子流",这些光子沿光的传播方向以 光速c 运动. 21 2 mhmvAν=+ 由能量守恒可得出: 爱因斯坦光电效应方程 A是电子逸出功 初动能及反向遏止电压与ν成正比,而与光强无关. 0 hA U ee ν = 截止频率 0 A h ν= 光强正比于单位时间流过单位面积的光子数.光 强越大,光子数越多. 00||kEeU h Aν== 光强正比于单位时间流过单位面积的光子数.光 强越大,光子数越多. 金属内电子吸收一个光子可以释放一个光电子.光 强越大,光电子越多,光电流越大. 电子吸收光子时间很短,只要光子频率大于截止 频率,电子就能立即逸出金属表面,无需积累能量的 时间,与光强无关. 爱因斯坦光子假说圆满解释了光电效应,但当时 并未被物理学家们广泛承认,因为它完全违背了光的 波动理论. The Nobel Prize in Physics 1921 "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect" 5b (=) : 0 ¨8 ZH K¨.Z +h rP'¨4§pü1915 HA rZ(· : / ¨h ,X ) A '< 7¨¨ A Z G $ ) A ,X!7.B~ The Nobel Prize in Physics 1923 "for his work on the elementary charge of electricity and on the photoelectric effect" Robert Andrews Millikan 1905年之后,爱因斯坦的研究风格发生了很 大的变化. 在建立广义相对论的过程中,爱因斯坦深入 学习了现代几何理论,并且形成了一个非常 强烈的观念,物理理论的简单和美是判断该 理论正确与否的最重要的依据. 'When I am judging a theory, I ask myself whether, if I were God, I would have arranged the world in such a way.' 此后爱因斯坦的最重要贡献是: 广义相对论的建立(1905年-1915年), 包括解释水 星近日点的剩余进动,光线的弯曲,宇宙学... 比热的量子理论(1906年) 辐射的量子理论(激光理论的基础,1916年) 波色-爱因斯坦凝聚(1924年, 2000年诺贝尔奖) 与玻尔关于量子力学的长期争论 统一场论(未完成,1923年-1955年)---《非对称 场的相对论性理论》(1954,《相对论的意义》附录) 0N (· :) 爱因斯坦1905年前的重要工作: 独立于吉布斯建立平衡态统计理论(1903年),并以 此申请伯尔尼大学博士学位未果. ae P $ 爱因斯坦和玻尔关于量子力学的 争论大大深化了人们对于量子力学 的理解. 在经历了多次失败后,爱因斯坦 承认量子力学是自恰的,但不完备. I still believe in the possibility of a model of reality that is to say, of a theory which represents things themselves and not merely the probability of their occurrence.' Quantum mechanics is very worthy of regard. But an inner voice tells me that this is not yet the right track. The theory yields much, but it hardly brings us closer to the Old One's secret. I, in any case, am convinced that He does not play dice.' (· :'G $ (= (· :,X EPR CB (· :,X Does the moon exist if nobody is looking at it Copenhagen interpretation: NO! The moon exists only in terms of probability wave functions Only when observed do these wave functions collapse to definite states Conflict between objective and subjective realities Einstein-Podolsky-Rosen (EPR) Paradox Decay of pion Electron and positron have opposite spins Let the electron and positron fly very far apart Measure the spin of one of them, say the electron This would instantaneously determine the spin of the positron Experimentally verified by Aspect (1982) Non-Locality of Quantum Mechanics Events in Region B instantaneously dependent upon events in Region A Events in Region A instantaneously dependent upon events in Region B widely separated regions Einstein: "Spooky action at a distance" Does this contradict special relativity In other words, can this be used to transmit messages faster than light NO! Because outcome is completely probabilistic We would never know in advance whether the electron is going to be spin up or down 爱因斯坦为挑战量子力学所提出的若干佯缪, 特别是EPR佯缪,事实上在1980年之后变成 了效应,而且成了量子计算,量子通讯的理论 基础. 量子保密通讯已经在全球多个地方实现,我国 也已经成功实现了在北京和天津之间的量子保 密通讯. I am a deeply religious non-believer This is a somewhat new kind of religion.' 'The belief in an external world independent of the perceiving subject is the basis of all natural science.' 'I cannot prove that scientific truth must be conceived as a truth that is valid independent of humanity; but I believe it firmly. I believe, for instance, that the Pythagorean theorem of geometry states something that is approximately true, independent of the existence of man. Anyway, if there is a reality independent of man, there is also a truth relative to this reality; and in the same way the negation of the first engenders a negation of the existence of the latter.' !,X 0x 1h H ※※※※※※ 无畏少年时 立志解团谜 孤苦求索路 荣辱两难知 |
