1) Waves Flashcards
what do waves do?
transfer energy and information without transferring matter
what happens with water and sound waves when travelling?
- wave travelling not sound/water
- eg if you drop a twig on water ripples come out but ripples don’t carry the twig or water
what is the frequency of waves?
- number of waves passing a a point per second
- Hz
what is wavelength?
- length of a full cycle of wave
- from one point to the same point on the next
what is wave amplitude?
-displacement from rest position to crest
centre to top of single wave
what is a wave period?
- number of seconds for one full cycle
- period= 1 / frequency
what are transverse waves?
- perpendicular waves (sideways)
- all electromagnetic waves
- S-waves (a seismic wave)
- ripples
what are longitudinal waves?
- parallel to direct waves
- sound waves, P-waves (a seismic wave)
- squash up and stretch out
what are 2 equations to work out wave speed?
V= D / t V= F X wavelengths (m)
V= wave speed m/s t= time (s)
how can you measure velocity of sound in air?
- set up oscilloscope with 2 microphones
- set with microphones together then move slowly away
- until waves on oscilloscope are equal
- mesure distance of microphones
- use V= F X wavelength
how can you measure velocity of ripples on water surfaces?
- use signal generator to make ripples
- use strobe light to make shadows
- alter generater into waves look still
- distance between wave= wavelength
- use V= F X wavelength
what happens when a wave is reflected?
- ‘sent back’ away from second material
- how echos are created
what happens when a wave is transmitted?
- second material
- carries on through new material
- used in communications, glass, lenses
what happens when a wave is absorbed?
- second material
- wave transferred energy into materials energy stores
- often thermal energy
what happens when a wave is refracted?
-wave changing directions at boundary
what is the process of a wave being refracted?
- waves different speeds in materials with different densities
- it boundary at angle, change direction
- greater change in speed, goes more bent
what do different materials do with varying wavelengths?
-absorb, transmit, refract and reflect I different ways
why does a ray diagram show?
the path that a wave travels
what is the normal on a ray diagram?
- line down middle
- boundary
what is the angle of incidence on a ray diagram?
-angle between normal and incoming ray
what is the angle of refraction?
-angle between normal and refracted ray
what is the method to investigate sound waves as vibrations in solids?
1.measure+record length of metal rod
2.set up clamps, hammer, microphone to computer
3. tap rod with hammer
4. record peak frequency
5. repeat to get average
6. calculate speed v=f X wavelength
wavelength= twice length of rod
what is the frequency of ultrasound?
above 20,000Hz
or 20KHz
what sound frequencies can the human ear hear?
20Hz to 20,000Hz
what are the uses of ultrasound?
- checking unborn babies
- sonar, on ships to detect fish
what are the uses of infrasound?
- elephants to communicate over long distances
- detect volcanic eruptions, volcanos release infrasound
