WAVES Flashcards
Define Amplitude:
Maximum displacement from equilibrium position
Define Frequency:
Number of complete oscillations per unit time
Define Period:
Time taken for one complete oscillation
Define Wavelength:
Distance between one point on a wave and a point with the same phase
on the next wave
Define Longitudinal wave:
Oscillations of the molecules are parallel to the direction of energy transfer, producing compressions and rarefactions
Define Transverse Wave:
Oscillations of the molecules/fields are perpendicular to the direction of energy transfer
Define Coherance:
When two waves have a constant phase relationship and the same
frequency
Define Path Difference:
The difference in the path lengths from the source to a point
Define Superposition:
When two or more waves meet at a point the resulting displacement is
equal to the vector sum of the individual displacements
Define Inteference:
When two coherent waves meet at a point and undergo superposition – the resultant amplitude is equal to the vector sum of the individual amplitudes
Define Constructive Inteference:
When the resultant amplitude is maximum (as the waves meet in phase)
Define Destructive inteference:
When the resultant amplitude is zero (as the waves meet pi out of phase)
Explain how an interference pattern is produced (eg. of bright and dark lines/loud and quiet
regions)
- Waves spread out from source, meet at points in undergo superposition
- When the waves meet in phase, with a path difference of n lambda, constructive interference occurs
- This constitutes a maximum amplitude of oscillation and bright spot/loud sound
- When the waves meet in antiphase/ 180 degrees out of phase, with a path difference of (n+1/2) lambda, destructive interference occurs
- This constitutes zero amplitude of oscillation and there is a dark spot/no sound
Define phase
The fraction of the wave cycle that has been completed relative to the origin
Define Path Difference
The difference in the distance travelled by two waves to a single point.
State the relationship between path difference and phase difference:
Path difference= (ie. multiply the fractional difference of the cycle completed by the wavelength)
Explain how a standing wave is set up:
- Two waves travelling in opposite directions
- Of equal frequency and similar amplitude
- Undergo superposition when they meet
- Constructive interference produces antinodes – positions of maximum amplitude
- Where waves meet in phase
- Destructive interference produces nodes – positions of zero amplitude
- Where waves meet in antiphase
Define node:
Positions of zero amplitude
Define antinode:
Position of maximum amplitude
State the conditions for a standing wave to be set up between a speaker and a wall
- The emitted and reflected wave must have similar amplitudes in order to completely destructively interfere and produce nodes
- So the wall should not absorb the wave
- The distance between the speaker and wall must be a whole number of half
wavelengths - There must not be multiple reflections from other parts of the room
State the distance between nodes in terms of the wavelength
Distance between nodes = λ/2
State the distance between antinodes in terms of the wavelength
Distance between antinodes = λ/2