[？糊涂了] 波动中能量守恒吗？（附：水面干涉条纹图片）

一、两个波的叠加

图1  波叠加的两种特殊情况

PPT - Physical Optics PowerPoint Presentation - ID:4446197

https://image2.slideserve.com/4446197/superposition-of-waves-n.jpg

https://www.slideserve.com/mika/physical-optics

   可见：两个同频正弦波，

   （1）同相位叠加，振幅可以增大一倍；

   （2）反相位叠加，波动消失了。

   疑问：

   波动的能量，怎么具体定义？如果按照振幅的平方/2定义，“反相位叠加，波动消失了”情况下，原来的能量去哪里了？

   上面是不是“能量守恒”的反例？

   《电工学》里通过定义“负量”来保证能量守恒。即：电感的无功功率为“正数”，电容的无功功率为“负数”。

   或者说，上面是“非惯性系”，里面“能量不守恒”？

图2  两个反相位正弦波相遇时，会出现什么现象？就是红圈附近的变化。

   一个类似的情况：假如上面图2两端是机械振动（正弦，反相位），中间的黑线是一根较长的有一定弹性的绳子。这是可以测量的一个场景。

   有没有人做过这个实体实验？

二、网上搜索到的3幅图片

   感谢原作者和有关人员！

图3  你看过双缝实验吗？

Have You Seen The Double Slit Experiment? - Page 2 of 2 - Shocking Science

https://ts1.cn.mm.bing.net/th/id/R-C.c22006a2fe9c5b5f06a262074d822c7f?rik=ftvOv0CPW6JQaQ&riu=http%3a%2f%2fwww.shockingscience.com%2fwp-content%2fuploads%2fsites%2f879%2f2015%2f12%2fpic1.jpg&ehk=mW0etMA8j%2fExlbn25QhfcLk9dcMel%2fQ09SB3WHPJtyY%3d&risl=&pid=ImgRaw&r=0

https://www.shockingscience.com/have-you-seen-the-double-slit-experiment/2/

图4  波干扰模式

Wave Interference Pattern

https://media.sciencephoto.com/image/c0279806/800wm/C0279806-Wave_Interference_Pattern.jpg

https://www.sciencephoto.com/media/705978/view/wave-interference-pattern

图5  显示相消干涉（暗线）和相长干涉（明线）的双缝干涉图案

Two slit interference pattern showing destructive interference (dark lines) and constructive interference (bright lines)

https://cpb-us-e1.wpmucdn.com/sites.ucsc.edu/dist/a/487/files/2016/01/main-qimg-75ebaf3dcce5031dbfd0c36426788499-1-171leep.jpg

https://ucscphysicsdemo.sites.ucsc.edu/physics-5b6b-demos/sound-interference-two-point-spacial/

    Explanation:

   This is a demonstration of the famous double-slit interference pattern, which was the forefront discovery of superposition in wavelengths. The experiment was first performed by Thomas Young in 1801, where he displayed incident light being shone upon two small cuts in a boundary. What he found is that the light wavelengths diffract through the slits and produce a pattern of interference (see Fig 1). This interference pattern produced lines of constructive and destructive interference called antinodes and nodes, respectively. (see Fig 1).

   这是著名的双缝干涉图的演示，这是波长叠加的最前沿发现。1801年，托马斯·杨（Thomas Young）首次进行了这项实验，他展示了入射光照射在边界上的两个小切口上。他发现，光波长通过狭缝衍射并产生干涉图案（见图1）。这种干涉模式产生了相长干涉线和相消干涉线，分别称为波腹和节点（波节）。（见图1）。 注：就是上面图5。

参考资料：

[1] Lecture 20: Interference of Waves, Beats

https://sites.ualberta.ca/~pogosyan/teaching/PHYS_130/FALL_2010/lectures/lect20/lecture20.html

[2] Albert Einstein. On the Method of Theoretical Physics [J]. Philosophy of Science, 1934, 1(2): 163-169.

doi：10.1086/286316 

https://www.jstor.org/stable/184387

   Pure logical thinking can give us no knowledge whatsoever of the world of experience; all knowledge about reality begins with experience and terminates in it. Conclusions obtained by purely rational processes are, so far as Reality is concerned, entirely empty. It was because he recognized this, and especially because he impressed it upon the scientific world that Galileo became the father of modern physics and in fact of the whole of modern natural science.    page 164

[3] 刘全慧，2022-12-10，相干波的能量佯谬

https://blog.sciencenet.cn/blog-3377-1367325.html

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