- Principle of Superposition
- Path difference
Here we go:
What is superposition?
Multiple waves passing through the same point.
What is interference?
The phenomena that occurs when waves superpose – it is described through the principle of superposition.
What is the principle of superposition?
“When multiple waves pass through a point, the resultant displacement at that point is equal to the sum of the displacements of individual waves at that point.”
Example: 2 Individual Waves Interfering
There are 2 Types of Interference:
|Constructive Interference||Crest + Crest OR Trough + Trough Displacements ADD UP to have a larger value Maximum displacement|
|Destructive Interference||Crest + Trough Displacements CANCEL OUT to have smaller value For identical waves, 0 displacement|
However, interference can happen between ANY waves as long as they are in the same medium.
Waves with different frequencies, amplitudes, or phase can interfere – the principle of superposition will be true: the resultant displacement = sum of individual displacements.
A Classic Example: 2 Wave Sources
When two point sources emit waves radially, the waves can interfere & form alternating patterns. This is due to path difference.
What is a path difference?
The difference in length travelled by 2 waves across a path from a SOURCE to a POINT where they superpose.
|When path difference is a WHOLE multiple of λ:||Maximum constructive interference|
|When path difference is an ODD multiple of λ/2:||Maximum destructive interference (antiphase)|
Now that you know the basics of interference & superposition, we can branch off into a few other sections: