Superposition and interference (Phase Difference (2 points on a wave with…
Superposition and interference
2 points on a wave with a phase difference of one pie radian or 180* are completely out of phase with each other, or anti-phase if you like.
Two points in a wave are both in phase if they are both at the same point in the wave cycle.
Points that are in phase have the same velocity and the same displacement.
Phase difference can either be measured in radians, degrees or fractions of a cycle.
360* = one full wavelength = 2pie radians
Superposition occurs when two or more waves pass through each other. At the moment the waves cross, the displacements due to each wave combine. Then each wave continues on, as they were before.
Resultant (total) displacement = sum of all of the individual displacements.
Superposition - one thing on top of another thing.
More Phase Difference
The phase difference between two waves is how far one wave lags behind another.
Two waves are in phase if they have a phase difference of 0 or a multiple of 360*.
The superposition of two or more waves results in interference.
When two waves meet, if their displacements are in opposite directions then they will cancel each other out. This is called destructive interference.
This is called total (completely cancelled out to the point of no wave) destructive interference.
A trough of the same negative displacement as a crest will be cancelled out to give no wave at all.
When two waves meet, if their displacement is going in the same direction (either up or down) the displacements combine to give a larger displacement.
This is known as constructive interference.
A crest and a crest gives a larger crest whilst a trough and a trough gives a larger trough.