【Daily Question】Theoretical Foundation 2020.05.28
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Multiple-choice question: A plane harmonic wave propagates in an elastic medium. As the elements of the medium move from their maximum displacement back to their equilibrium position, ( ) (A) its kinetic energy is converted into potential energy. (B) Its potential energy is converted into kinetic energy. (C) It obtains energy from an adjacent segment of the medium element, and its energy gradually increases. (D) It transfers its energy to the adjacent element of the medium, which gradually decreases. Answer: C Hint: An extra reward will be given to those who can explain the solution process; the answer can be seen there!
This post was last edited by h20090630 on 2020-5-28 at 13:22. The energy variation of a C-wave is different from that of vibration; during wave propagation, when the elements of the medium are at their equilibrium positions, kinetic energy, potential energy, and total mechanical energy are all at their maximum values. At the point where the displacement of the medium element is maximum, all three are zero. Thus, each volume element of the wave continuously absorbs energy from the previous particle and then passes it on to the next particle.