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I have been using David Morin' drafts on waves along with French's wave book and Fox Smith's book for my undergrad wave course and one thing I don't understand is the physical intuition behind reflection from a free end. I understand the boundary conditions and the mathematics but a couple of things I can't understand how they physically actually happen:

  1. In French's book he says that the incoming upward pulse causes the massless ring to apply an equal reaction force but in upward direction, but shouldn't it be downward?

  2. If the boundary conditions require that the massless ring be always horizontal and hence apply no transverse force then how is it supposed to create a total upward reflected wave?

  3. So can anyone explain me what is the physical intuition behind reflection from free end as in what actually physically happens and how the forces play out to create the upright reflection?

Note: please don't mark my question as duplicate because I have already searched the forum and none of the related questions have my answer and also there is a related question but no one has answered. So please consider my question.

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    $\begingroup$ Did you see the answer I had given here: physics.stackexchange.com/q/300581 $\endgroup$
    – user137289
    Commented Mar 30, 2019 at 21:15
  • $\begingroup$ Yes I saw it, but I don't want an answer with image pulse/wave.. I want an actual description $\endgroup$
    – Metric
    Commented Mar 30, 2019 at 21:27
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    $\begingroup$ For me, that animation provides to intuition about a reflection from a free end. What is it that is surprising to you? Does it make sense to you that there is no reflection from a continuous string going out of the window as in the PhET simulation? Do you find it strange that a free end acts differently? That it would go up twice as far as the amplitude? $\endgroup$
    – user137289
    Commented Mar 30, 2019 at 21:53
  • $\begingroup$ No I didn't mean that, by intuition I do not mean whether I find it strange or not. I hope to understand in physical terms as to what is actually happening as in how the reaction forces or other forces cause the reflection $\endgroup$
    – Metric
    Commented Mar 31, 2019 at 4:05

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Ah well, I will try. Consider a pulse traveling on a string to the right. The string terminates at a ring that is free to slide on a vertical pole. There, the upward force on the ring due to its neighbors on the left is the same as for any point. But the mass to be lifted is only half as large, so it flies up twice the amplitude.

Tension then pulls the ring down. The pulse then travels to the left, in just the same way as someone had moved the ring.

This interactive simulation is really good: https://phet.colorado.edu/en/simulation/wave-on-a-string

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  • $\begingroup$ Well thanks that you at least tried to help me.. the general attitude of the people out here is very disheartening, most of them think that questions like this are somehow trivial and not worth answering and only understanding the mathematics behind a physical phenomenon is enough. I want understand both the mathematical structure of the problem as well as the physical process behind it, but most people here have no regard for that. I saw another very similar question in this forum that had not been answered or even attempted by anyone and that's sad to see $\endgroup$
    – Metric
    Commented Mar 31, 2019 at 9:42

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