Waves 1 Flashcards
Define a longitudinal wave
a wave where the plane of oscillation of particles is parallel to the direction of energy propagation
Give two examples of longitudinal waves
1) sound waves
2) P-waves
Define a transverse waves
a wave where the plane of oscillation of particles is perpendicular to the direction of energy propagation
Give two examples of transverse waves
1) EM waves
2) water waves
3) S-waves
Define a progressive wave
a moving wave that carries energy from one place to another without transferring any matter
Define the amplitude of a wave
the maximum displacement of the wave from equilibrum
Define wavelength
the shortest distance between two points in phase
Define time period
the time taken for one whole wavelength to pass a point
Define frequency
the number of whole wave cycles passing a given point per second
Define a polarised wave
a wave in which all the vibrations are in one plane, perpendicular to its direction of propagation
Define polarisation
restricting a wave’s oscillations to one plane, perpendicular to its direction of propagation
How do you show an unpolarised wave in a drawing?
1) an up and down arrow with a dot in the middle
OR
2) arrows going all directions out from the centre
How do you show a polarised wave in a drawing?
an up and down arrow
Define phase
a measurement of the position of a certain point on a wave cycle (measured as an angle or in fractions of a cycle)
Define phase difference
the amount by which one wave lags behind another (measured as an angle or in fractions of a cycle)
If two points are in phase, what is their phase difference?
0
If two points are in antiphase, what is there phase difference?
π radians
When does superposition occur?
- when two (or more) waves overlap/interfere
- the resultant wave is the sum of the displacements of the original waves
What are the two types of interference?
1) constructive
2) destructive
When does constructive interference occur?
when two waves are in phase
When does destructive interference occur?
when two waves are in antiphase
Define a stationary/standing wave
- a wave formed when two progressive waves travelling in opposite directions superposition
- their wavelengths (and frequencies) must be equal and their amplitudes similar
What must the length of the string equal in terms of λ in order for a standing wave to be seen?
length = (nλ)/2
n = 1, 2, 3, …
Define a node
a point of minimum amplitude on a standing wave
Define an antinode
a point of maximum amplitude on a standing wave
How do you represent an antinode?
x
How do you represent a node?
.
Is there energy transfer in a standing wave?
no
energy is stored
What does μ equal in the equation: f=(1/2l)x√(t/μ)?
mass per unit length
What does l equal to in the equation: f=(1/2l)x√(t/μ)?
distance between outermost nodes
List 5 properties of a standing wave
1) no energy transfer along the wave
2) internodal distance = λ/2
3) points between two adjacent nodes are all in phase
4) points between two adjacent nodes are in antiphase with the points between the neighboring adjacent nodes
5) a whole number of (λ/2)s fit onto the string
