Waves of the
same frequency that arrive at the
same point at the same time may be
in phase or out
of phase.
The red and green waves in Graph 1 are exactly in phase.
constructive interference
The orange and magenta waves in Graph 2 are exactly out of phase.
total destructive interference
The
wave that results from
superposition of two waves that are in phase has the
same frequency and wavelength as the two original waves, but it has a
different amplitude.
If the waves interfere constructively (as in Graph 1), the amplitude of the resulting wave is the sum of the amplitudes to the two waves.
Waves that arrive at the same point
out of phase are said to
interfere destructively.
The amplitude of a wave resulting from destructive interference is the difference between the amplitudes of the two waves.
If the waves have the same amplitude (as in Graph 2), they cancel one another.
If the waves have different amplitudes (as in Graph 3), the resultant wave has a reduced amplitude.
partial destructive interference