Phase and Path Difference

There is a very simple relationship between the phase and path difference.

A whole wavelength corresponds to one whole oscillation, a path difference ofThis is turn corresponds to a phase difference ofor 360 °. Confusion arises because many waves are sinusoidal so the displacement from equilibrium is given bywhereso whenincreases byincreases 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

45°

90°

135°

180°

225°

270°

315°

360°

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