wave behaviour - basics Flashcards
Define ‘wave’
A vibration which transfers energy without transferring matter
define ‘transverse’
oscillations are perpendicular to the direction of propagation
define ‘longitudinal’
oscillation are parallel to the direction of propagation
Made up of compression and rarefactions
define ‘wavelength’
distance from one point on a wave to the same point on the next wave, measured in metres
(eg. crest to crest or trough to trough)
define ‘period’
Time taken for a whole wave to pass a specific point
What is the symbol for period
T
What is the equation for period?
T = 1/F
define ‘frequency’
How many waves pass a certain point per second, measured in Hertz, Hz
What is the equation for frequency?
F=1/T
What is the equation for wave speed?
frequency x wavelength
define ‘amplitude’
Maximum distance from the undisturbed position (ie rest to crest or trough)
define ‘displacement’
The distance of a particle of the wave from equilibrium at any one time
What is the maximum displacement of a wave?
The amplitude
Which kind of graph is used to work out frequency?
displacement-time graph
Which kind of graph is used to work out wavelength?
displacement-distance graph
What is a radian?
The angle in a circle where the arc has the same length as the radius
What is 360 degrees in radians?
2π
What is 180 degrees in radians?
π
What is 90 degrees in radians?
π/2
What is superposition?
When waves in the same place pass through each other, creating a resultant amplitude at that point without affecting one another. The resultant amplitude is the sum of the two wave’s amplitudes. This can be smaller or larger than the original amplitudes.
What are phasors?
A method of describing waves by showing where a wave is in its cycle, using an arrow in a circle rotating anticlockwise.
In phasors, what does the length of the arrow represent?
wave amplitude
In phasors, what does the speed of rotation represent?
wave frequency
In phasors, what is one wavelength?
A full circle rotation (360 degrees or 2π radians)
What is the equation for angular speed?
2π/t or 2πf
What is the symbol for angular speed/frequency?
ω (omega)
What is angular frequency measured in?
radians^-1
What is the equation for distance traveled in radians?
angular frequency x time
In a phasor diagram, what is the displacement?
The opposite
A x sinӨ
What is happening when two waves are in phase?
There is no phase difference, waves do the same things at the same time
What is the phase difference when waves are in phase?
0 or 360 degrees
What is happening when waves are in antiphase?
Waves do completely opposite things at the same time
What is the phase difference when waves are in antiphase?
180 degrees
If one wave is at its maximum and one is at rest, what is the phase difference?
90 degrees
What does it mean when waves are coherent?
Waves have the same frequency and constant phase difference
What is the symbol for phase difference?
Φ
What is a phasors position when a wave goes down through rest?
90 degrees pointing left
What is a phasors position when a wave goes up through rest?
90 degrees pointing right
