In the above video we study the reflection of a wave at a fixed end.
The blue line at the bottom of the video indicates
the position of the front of the reflected pulse.
Notice that after reflection the incoming wave and the reflected wave
interfere with each other in such a way
that at some places the amplitude becomes twice as large,
but at other places the amplitude vanishes.
However, besides that we observe only oscillations
in the part where the two waves interfere.
No wave seems to move to the left or to the right.
That phenomenon is called a
standing wave.
In particular the red object does not move
at all in this example,
whereas the blue object oscillates more heavily
when the two waves interfere than when just the incoming wave passes by.
At the fixed end the amplitude must be zero by definition.
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