Chapter 8 - Waves Flashcards
What is a longitudinal wave ?
A longitudinal wave is one in which the particles vibrate parallel to the direction in which the wave is travelling
Name 4 types of longitudinal waves
- sound waves
- ultrasound waves
- slinky spring waves
- p-type earthquake waves
What are compressions ?
A place where the particles bunch together
What are rarefactions ?
Are places where the particles are furthest apart
What is a transverse wave ?
A transverse wave is one in which the vibrations are at 90*
Give some examples of transverse waves
- water waves
- waves on strings and ropes
- electromagnetic waves
Name 3 ways how you can prove that waves carry energy
- water waves can be used to generate electricity
- loud sound waves can cause things to vibrate
- microwaves make things heat up
What is the frequency of a wave ?
The frequency of a wave is the number of complete waves passing a fixed point in a second
What are the units for frequency ?
Hz (hertz)
What is the wavelength ?
The wavelength of a wave is the distance between two consecutive crests or troughs
What is wavelength measured in ?
measured in meters and the symbol is ‘landa’
What is the amplitude of a wave ?
The amplitude of a wave is the greatest displacement of the wave from its undisturbed position
What is the unit of amplitude ?
meters, m
How do you find the wavelength in a longitudinal wave ?
It is found by measuring the distance from one compression to the next
What is the equation for wave speed ?
wave speed = frequency x wavelength
What properties does a wave reflected off a barrier have ?
- the angle of incidence = the angle of reflection
- the wavelengths are equal
- the frequencies are equal
- there is continuity of incident waves and reflected waves at the barrier
How does changing the depth of the water change how quickly waves can travel through it ?
Waves can travel more slowly through shallower water
the frequency of water travelling through shallow and deep water are equal, so the shallower water must have a shorter wavelength
What should be noted when water travels through deep water ?
- angle of incidence in deep water is always bigger than the refraction of shallow water
- wavelength and speed of waves in deep water are greater
- frequencies are the same
- there is continuity of incident and refracted waves at the boundary
What is the analogy between water and light waves?
True for both water wavs and light
- angle of incidence = angle of reflection
- reflected wavelength = incident wavelength
- reflected frequency = incident frequency
- reflected speed = incident speed
- the refracted wavelength is less than the incident one
- the refracted speed is less than the incident speed
What is the range of audible sound ranges
2Hz to 20000Hz
What is sound above 20000Hz called ?
ultrasound
Name three ways how humans use ultrasounds
- scanning soft tissues to diagnose cancers
- locating fish by seagoing trawlers
- mapping the surface of the ocean floor
Explain an application of ultrasound in medicine
- the probe sends out ultrasound rays and records reflections
- ultrasound can be sent out in a very narrow beam
- by examining the reflections the computer builds up a picture of the foetus
How is ultrasound used in scanning metal castings ?
- special devices fitted to a railway track
- ultrasound passes through the track
- if there is a crack or flaw it can be imaged by a computer
