Since the fifth reflection
erased the oscillatory movements of all the previous reflections
and the incoming wave,
the sixth reflection
has to start from zero and thus
causes the same oscillatory movements as the incoming wave,
the seventh reflection
causes the same oscillatory movements as
the first reflection,
etcetera.
Every time after six reflections
the oscillatory movements of all the previous reflections
and the incoming wave are erased.
The reason for this phenomenon is that the wave does not fit well
in the space between the fixed ends.
Remember that the space between the fixed ends corresponds
to 3.33 times the wavelength.
In the next video we study what happens when the space
between the fixed ends corresponds
to exactly 4 times the wavelength.
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