关于机械横波反射与折射的演示实验

A DEMONSTRATION EXPERIMENT ON REFLECTION AND REFRACTION OF A MECHANICAL WAVE

本文介绍了通过改变筷波仪部分区段振子单元转动惯量的方法,使筷波仪振子链成为波阻抗不同的两个区段。在低阻抗区段的一端激发使振子链中形成机械波时,机械波将在阻抗突变点发生反射和折射。如果在下游高阻抗区段的尾端部安置适当的阻尼完全吸收折射波列的能量,则在下游高阻抗区段就会只有一列折射波行波;而在上游区段的波场则是入射波与反射波的叠加。叠加的结果,在上游低阻抗区段则表现为一列与折射波在阻抗突变点十分吻合的行波和一列在阻抗突变点是波节(高阻抗反射)或波腹(低阻抗反射)的驻波的叠加。

By changing the moment of inertia of the vibrator unit in some sections of chopsticks wave instrument,the vibrator chain of chopsticks wave instrument is made into two sections with different wave impedance.When a mechanical wave is excited at one end of the low impedance region to form a mechanical wave in the oscillator chain,the mechanical wave will reflect and refract at the abrupt point of the impedance.If an appropriate damping is placed at the tail end of the downstream high impedance section to fully absorb the energy of the refracted wave train,there will be only one refracted wave train in the downstream high impedance section;and the wave field in the upstream section is the superposition of the incident wave and the reflected wave.The result of superposition shows that in the upstream low impedance region,a series of traveling waves which are very consistent with the refraction wave at the impedance mutation point and a series of standing waves which are the nodal(high impedance reflection)or the antinode(low impedance reflection)at the impedance mutation point.