Waves Flashcards
What direction does a wave transfer its enrgy
The direction they are travelling
What is the amplitude of a wave
Maximum displacement of a point on the wave formats undisturbed position
Distance of crest or trough to distance
What is the wavelength of a wave
Distance between the same point on two adjacent waves (e.g. trough to trough)
What is the frequency of a wave
Number of completed waves passing a certain point per second
Measure in hertz
1 hertz =1 wave per seconf
Transverse wave move in a
Perpendicular vibrations
Remember TRANSVERSE over a mountain
Examples of transverse waves
All extranets waves
Ripples and waves in water
A wave on a string
Longitudinal waves move in a
Parallel direction to the energy transfer
Remember LONGitudinal moves aLONG the energy
they squash up and strech out the arrangements of particels int he medium they pass through making comptessions ( high pressure,lots of particles) and rarefactions (low pressure)
Examples of longitudinal waves
Sound waves
Shock waves
How do u calculate wave speed
Wave speed = frequency x wavelength
How do you measure the speed of sound
With an eye oscilloscope
Set up oscilloscope so that the detected waves at each microphone are shown as separate waves
Start with both microphones next to the speaker then slowly move away until two waves are aligned on the display bait have moved one wavelength apart.
Measure distance between microphones to find one wavelength.
Find speed using formula v= f x wavelength
Measure the Speed of wave ripples using a strobe light ( practical)
signal generator attached to a dipper of a ripple tank creates water waves at a set frequency.
turn on strobe light and you will see shadows in a wave pattern of the waves crest.
alter frequency of the strobe light until the wace pattern on the screen appears to freeze and stop moving. this happens when frequency of waves is equal to the frquency of the srobe light.
the distance between each line is one wavelength. measure distance between 10 and find average
use v=f wavelength
how do you find speed of waves in solid
Use peak frquency of sound waves when you hit an object ‘rod with hammer’. hitting the rod causes waves to be produced along the rod. the vibrations create sound waves in the air around it. These sound waves have same frequency as waves in the rod.
1) measure length of a metal rod
2) secure rod at centre with clamps holding elastic bands and a microphone to record.
3) tap rod with hammer abd write down peak frequency displayed on computer.
4) repeat to find average
5) use v=f x wave length where wavelength is twice length of rod
When a wave arrives at a barrier what can it do
Be absorbed, transmitted- continue travelling through the material, reflected
What do you need to include in a simple ray diagram for reflection
Angle of incidence = angle of reflection
Angle of incidence is the angle between the incoming wave and the normal
Angle of reflection is angle between the reflected wave and normal
The normal is imaginary line perpendicular to the surface that the point of incidence hits
What is speculator reflection
When a wave is reflected in a single direction by a smooth surface.
What is diffuse reflection
When waves reflected on rough surface and the rays are scattered in lots of directions.
Why does diffuse reflection occur
As normal is different for each day which means the angle of incidence is different. Therefore the angle of reflection is different
What is refraction
Waves changing direction at a boundary
Explain refraction
How much it is refracted depends on how much the waves speeds up or slows down which is usually due to the density of the object.
If a wave crosses a boundary and slows down or will bend towards the normal.
If it speeds up it will bend away from the normal.
if travelling along normal it will change speeds bit not refract
optical density is measured by how quickly light can travel through it.
where do you do a light experimrbt
in a dim room
how can u use transparent materials to investogate refraction (practocal)
1) place a rectangular glass box and trace around it.
how are sound waves caused and travel
by objects vibrating
vibrations are passed through surroundings as a series of compressions and rarefactions.
it causes particles in solids to vibrate.
However not all frequencies of sound can transfer through objects.
what factors affect if sound can travel through an object
their SIZE, SHAPE and STRUCTURE.
how does wavelength change as waves travel through different mediums
frequency doesn’t change
due to v= f wavelength
the wavelgth changes as it get longer when wave speeds up and shorter when it slows down
why is there no sound in space
as sound waves can’t travel through a vacum
how does the ear work to hear using sound waves
sound waves that reach your eardrum cause it to vibrate.
these vibrations are passed on to tiny bones called osscicles, through the semicircular canal and to the cochlea.
the cochlea turns these vibrations to electrical signals that get sent to the brain.
what is the little bones in the ear called
ossicles
what turns vibrations into electrical signals in your ear
cochlea
How does the frquency of sound waves change the brains interpretaion of the signals as sounds
higer frequency the higher pitch
higher intensity louder
what is ultra sound
sound with a frquency over 20,000 hz
what happens to ultrasound at boundaries
the waves get partially reflected.
1) when wave enters a new medium some of the wave is reflected off the boundary and some it transmitted (refracted)
2) you can fire a short pulse of ultrasound at an object and wherever there are boundaries between one substance and another some of the ultrasound is reflected back.
3) time taken for the reflection to reacha detetor tells you how far away the boundary is
uses of ultrasound
medical imaging and industrial imaging
how is ultrasound used in medical imaging
ultrasound waves can pass through the body but when reaching a boundary is reflected back.
the timing and distribution of these echoes are processed by a computer to produce a video image of the foetus.
completely safe
how is ultrasoud used in industrial imaging
used to find flaws in objects such as pipes or materials like wood.
waves relect at a different distance form normal when a crack is present.
what is infrasound
sound lower than 20 hz
animals use it to comunicate and volcanoes, avolanches and earthquakes also produce infrasound
how is ulrasound used in radars
boats uses echo sounding, used to find out the distance from seabed or to locate objects deep underwater.
time taken divide by 2 as has to go there and back
what causes seismic waves
earthquakes and explosions
P waves are
longitudinal
travel through solids and liquids
travek faster than s waves
S waves are
transverse
only travel through solids
slower than P waves
how do seismic waves (infrasound waves) help the exploration of earths core
by ovserving how waves are absorbed and refracted scientists can work out where the properties of the earth changes dramatically.
