There is a very simple relationship between the phase and path difference.
A whole wavelength corresponds to one whole oscillation, a path difference of
This is turn corresponds to a phase difference of
or 360 °. Confusion arises because many waves are sinusoidal so the displacement from equilibrium is given by
where
so when
increases by
increases by
The angle however may also be measured in degrees so a phase difference of %pi means the same as a phase difference of 180°, and both of these are equivalent to a path difference of
The following table shows equivalent path and phase difference for different phase/path differences.
|
Path difference |
Phase Difference in Degrees |
Phase Difference in Radians |
|
0 |
0° |
0 |
|
|
45° |
|
|
|
90° |
|
|
|
135° |
|
|
|
180° |
|
|
|
225° |
|
|
|
270° |
|
|
|
315° |
|
|
|
360° |
|
