# Wave reflected on a hard wall

1. Nov 24, 2015

### simon96c

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. Nov 24, 2015

### .Scott

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.

3. Nov 25, 2015

### simon96c

That helped a lot!