Answer:
Explanation:
A particular solution for the 1D wave equation has the form

where A its the amplitude, k the wavenumber, ω the angular frequency and φ the phase angle.
Now, for any given position  , we can use:
, we can use:

so, the equation its:
 .
.
This is the equation for a simple harmonic oscillation!
So, for any given point, we can use a simple harmonic oscillation as visual model. Now, when we move a  distance from the original position, we got:
 distance from the original position, we got:

and

now, this its



So, there its a phase angle difference of  . We can model this simply by starting the simple harmonic oscillation with a different phase angle.
. We can model this simply by starting the simple harmonic oscillation with a different phase angle.