# Superposition and coherence

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• Created by: apple87
• Created on: 25-05-15 11:34
When does superposition happen?
When two or more waves pass through eachother.
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What happens at the instant the waves cross?
The displacements of each wave combine.
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What type of interference do you get when a trough meets a trough or a crest meets a crest?
Constructive interference.
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What does a trough plus a crest of equal size give, and which type of interference is this?
Nothing- the waves cancel eachother out. Destructive interference
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Which way do phasors rotate?
Anti-clockwise.
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What does the length of the phasor arrow show?
Amplitude
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How do you find the resultant amplitude using phasors?
Add the phasors tip to tail.
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When are two waves in phase?
If they are both at the same point in the wave cycle.
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What is it called when waves are exacly out of phase?
Antiphase
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Waves that are in phase have a phase difference of what?
0 or multiple of 360
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Waves that are exacly out of phase have a phase difference of what?
180
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To get interference patterns two sources must be what?
Coherent
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When are two sources coherent?
When they have the same wavelength and frequency and a fixed phase difference between them.
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What does constructive and destructive interference depend on?
Path difference
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What is the formula for constructive interference?
Path difference= n x wavelength (Where n is an integer)
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What is the formula for destructive interference?
Path difference= (2n+1) x wavelength / 2 = (n+1/2)wavelength
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## Other cards in this set

### Card 2

#### Front

What happens at the instant the waves cross?

#### Back

The displacements of each wave combine.

### Card 3

#### Front

What type of interference do you get when a trough meets a trough or a crest meets a crest?

### Card 4

#### Front

What does a trough plus a crest of equal size give, and which type of interference is this?

### Card 5

#### Front

Which way do phasors rotate?