3.1 Longitudinal & Transverse Waves Flashcards
What is a progressive wave defined as?
A wave that transfers energy from one point to another without transferring the medium itself
What are the properties of a progressive wave? (6(
- displacement
- amplitude
- wavelength
- time period
- frequency
- speed
What is the displacement of a wave?
- distance of a point on the wave from its equilibrium position
What is the Amplitude of a wave?
- the maximum displacement of a particle in the wave from its equilibrium position
What is the wavelength of a wave?
- the distance beterrn points on successive oscillations of the wave
- measured in metres
What is the time period of a wavE?
- the time taken for one complete oscillation or cycle of the wave
- measured in seconds
What is the frequency of a wave?
- the number of complete oscillations per unit time
- measured in Hertz
What is the equation for frequency?
frequency = 1/time period
What is the speed of a wave?
- the distance travelled by the wave per unit time
- (metres per second)
What is the wave equation?
speed of a wave = frequency x wavelength
What does the wave equation show?
as the wavelength increases, the frequency decreases and vis a versa
What is phase difference?
the phase difference between two waves is a measure of how much a point or wave is in front or behind another
how can you find the phase difference?
- the relative position of the crests or troughs of two different waves of the same frequency
What determines whether 2 waves are in or out of phase?
- when crests and troughs are aligned in phase
- when crest of one wave aligns with the trough of another they are in anti phase
How can the phase difference be calculated?
- from 2 different points on the same wave
- same point on 2 different waves
How can phase difference be measured?
- fractions of a wavelength
- degrees
- radians
if a wave is in phase, how can it be described?
- 360 degrees
- 2π radians
if a wave is in anti-phase, how can it be described?
- 180 degrees
- π radians
What are the 2 types of waves?
- transverse
- longitudinal
How can you determine what type of wave a wave is?
by the direction of the oscillations in relation to the direction the wave is travelling
What is a transverse wave?
a wave in which the particles oscillate perpendicular to the direction of the wave travel and energy transfer
What are the properties of transverse waves?
- show areas of crests and troughs
- can be shown on a rope
- can be polarised
What are 2 examples of transverse waves?
- electromagnetic waves
- vibrations on a guitar string
- waves on a string
- seismic waves
Longitudinal wave is defined as:
a wave in which the particles oscillate parallel to the direction of the wave travel and energy transfer
What are some characteristics of longitudinal waves?
- shows areas of compressions and rarefactions
- shown on a link spring
- cannot be polarised
How is energy transmitted in a longitudinal wave?
- the medium vibrating as they are given energy
- compressions cause the nearby particles to also vibrate with more energy
- produces a compression further along in the medium
What are examples of longitudinal waveS?
- sound waves
- ultrasound waves
- waves through a slinky
- seismic waves
What are compressions of a wave?
regions of increased pressureW
What are rarefactions of a wave?
regions of decreased pressure
What is polarisation?
when particles oscillations occur in only one of the directions perpendicular to the direction of wave propagation
Why can polarisation only occur in transverse waves?
because transverse waves oscillate in any plane perpendicular to the propagation direction
What does it mean when transverse waves are polarised?
- vibrations are restricted to one direction
- vibrations here are still perpendicular to the direction on propagation/energy transfer
Why can longitudinal waves not be polarised?
- they oscillate parallel to the direction of travel
How can waves be polarised?
through a
- polariser
- polarising filter
How do polarisers work?
they only allow oscillations in a certain plane to be transmitted
what are some examples of polarisation?
- sunglasses
- photography
- radio and microwave signals
How do polaroid sunglasses work?
- they contain lenses with filter transmission axes that are vertically oriented
- the glasses don’t allow any horizontal polarised light to pass through
- when light is reflected from a surface it undergoes partial polarisation
- thus the glasses reduce the glare on the surface allowing things to be viewed more clearly
What is partial polarisation?
if the surface is horizontal, a proportion of the reflected light will oscillate more int he horizontal plane than in the vertical plane
How does Polaroid Photography work?
- work in the same way as glasses
- allow photographers to take photos of objects underwater
How can polaroid cameras take photos underwater?
- light reflected on the surface of the water is partially polarised in the horizontal plane
- the glare is eliminated by the polarising lens
- light from underwater objects is refracted by the surface of the water thus not plane polarised
- thus the light from the underwater object is more intense than the glare and how’s up much more brightly in the photo
How does polarisation of radio and microwave signals occur?
- radio and television services are broadcast either horizontally-polarised or vertically-polarised
- the reception aerial needs to be mounted flat or on its side
- the orientation of the aerial wall depend on the transmitter it is pointing towards and the polarity of the services being broadcast
