Wave Properties ( 2 ) Flashcards
What is the super position effect?
- When waves meet, they pass through each other
- At the point where they meet, they combine for an instant before they move apart
- Combining effect is super position
What happens when waves cross?
- Displacements due to each wave combine.
* Then each wave separates and continues their path
What is the principle of superposition?
When two waves meet, the total displacement at a point is equal to the sum of the individual displacements at that point
What happens when a crest meets a crest?
A supercrest is created, two waves reinforce each other
What happens when a trough meets a trough?
- Super trough is created
* Two waves reinforce each other
What happens when a crest meets a trough of the same amplitude?
- When a crest meets a trough of the same amplitude, the resultant displacement is zero
- The two waves cancel each other out
What is a minimum?
If a crest meets a trough that is not exactly the same amplitude, the resultant is called a minimum
When are stationary waves formed?
When two waves are continuously sent from either end.
What are progressive waves?
Two sets of waves, term is used in order to distinguish from stationary waves.
What is constructive interference?
Two waves reinforce each other
What is destructive interference?
Two waves cancel each other out
What is a node?
Point of no displacement
What is the phase at each node?
At each node along the stationary wave, the two sets of waves are always 180 degrees out of phase, so they cancel each other out.
What is interference?
- As waves are continuously through each other at constant frequency and at constant phase difference, cancellation and reinforcement occurs at fixed position
- This is known as interference
What interference pattern do coherent waves produce?
- Coherent sources of waves produce an interference pattern where they overlap
- Because they vibrate at the same time with a constant phase difference
What happens if phase difference is changed at random?
- Points of cancellation and reinforcement would move about at random
- No interference pattern would be produced
When are two points in phase?
• When they are both at the same point in the wave cycle
• Points in phase have the same displacement and velocity
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What is the phase difference of points in phase?
• Zero
or
• Multiple of 360 degrees ( full cycle )
What is the phase difference of points not in phase?
• Odd number multiples of 180 degrees ( half cycles ) are exactly out of phase
What is required to get clear interference patterns?
Two or more sources must be coherent and in phase
When are two sources coherent?
• Same wavelength, frequency and a fixed phase difference between them
