I have belatedly seen your queery about phase.  In the  abstract their is
no answer to your question for phase reqires a reference i.e the phase of
something relative to ....???     (i.e another part of the wave).   In the
limit the phase must always close;  Nature abhors odd bits of phase (see
papers in J. Inst Phs and M.N.R.A.S. by a chap called  Jennison, c1960) it
is now known as the principle of Phase Closure.
73, Roger,  G2AJV.