Note that we will get the same wave if we
change the phase of a sinusoidal wave by an integer multiple of 2
p rad or we shift a sinusoidal wave by a distance equal to an
integer multiple of l. For example,
a phase difference of 10.2 p rad is
equivalent to a phase difference of 0.2 p
rad and a path difference of 5.1 l is
equivalent to a path difference of 0.1 l.