## 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° | 0 |

45° | ||

90° | ||

135° | ||

180° | ||

225° | ||

270° | ||

315° | ||

360° |