3.4 Superposition and Interference Flashcards
When does superposition happen?
When two or more waves pass through each other
At the instant that the waves cross, the displacement due to each wave combine, then each wave continues on its way
What does the principle of superposition say?
When two or more waves cross, the resultant displacement equals the vector sum of the individual displacements
How can you use superposition to simplify waves?
A complex wave can be separated into several simple sine waves of various sizes
What is interference?
The superposition of two or more waves can result in interference
Interference can be either constructive or destructive
What is constructive interference?
When two waves meet, if their displacements are in the same direction, the displacements combine to give a bigger displacement (a crest plus a crest gives a bigger crest etc)
What is destructive interference?
If a wave with a positive displacement meets a wave with a negative displacement, they will undergo destructive interference and cancel each other out
How do you find the displacement of the combined waves in superposition?
Add the displacements of the two waves
What does it mean when two points on a wave are “in phase”?
Two points on a wave are in phase if they are both at the same point in the wave cycle
Points in phase have the same displacement and velocity
What does it mean when two points have a phase difference of 360 degrees?
Two points with a phase difference of zero, 360 or a multiple of 360 degrees are in phase
How would two waves be in phase?
If their phase difference is 0 or a multiple of 360 degrees
This usually means both waves come from the same oscillator
