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Wave reflected on a hard wall

  1. Nov 24, 2015 #1
    Hello everyone,
    I am currently studying traveling waves and reflection but I didn't understand a part of my last lesson.
    If we consider a string with a loose end and the other end attached to a wall we expect the string to have zero displacement at the wall and to have a reflected wave "-f(-x-vt)" (given that the incident wave is f(x-vt) ).
    My question is probably really silly, but I can't understand why the reflected wave is "-f(-x-vt)" and not "-f(x+vt)" (travelling in the other direction, with inverted amplitude).

    I hope I chose the right section since this is my first post here!
    Thanks in advance to anyone who will reply to this (probably) really silly question!
  2. jcsd
  3. Nov 24, 2015 #2
    Lets say that the wave has the shape that matches the side profile of a shoe. The -f flips the profile up-side-down. The -x changes the direction the wave is moving. But we still want the wave to move toe first, so the -vt has to stay -vt.

    Hope that helps.
  4. Nov 25, 2015 #3
    That helped a lot!
    Thank you very much for your reply.
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