⭐️Topic SP4 - Waves Flashcards
What are transverse waves?
Waves where the particles move up and down at right angle to wave direction
Give some examples of transverse waves
Water waves, S waves and em waves
What are longitudinal waves?
Where particles in the material move parallel to the direction of wave travel
Give examples of longitudinal waves
Sound waves, p waves
What’s a difference between transverse and longitudinal waves?
Transverse waves don’t need a medium to travel through but longitudinal waves do
What is the wave frequency and it’s unit?
The number of waves passing a point each second in Hz
What does frequency determine for sound and light?
In sound, it determines the pitch and light it determines the colour
What is the period?
The length of time taken for wave to pass a given point
What is wavelength and give it’s unit?
The distance from one point of a wave to the same position on the next point of the wave in meters
What is amplitude and give the unit?
The maximum distance of a point on the wave away from its rest position. (Greater the amplitude, the louder the sound) Measured in meters
What is velocity of a wave?
The speed of a wave in the direction its travelling.
How do you calculate wave speed using distance and time?
Speed (m/s) = distance (m) / time (s)
How do you calculate wave speed in terms of frequency and wavelength?
Wave speed (m/s) = frequency (Hz) x wavelength (m)
Where does refraction of a light ray occur?
At the interface between the two mediums
When light from air to glass or water,
It refracts towards the normal
When light goes from a more dense medium to a less dense one,
It refracts away from the normal
Why does light refract when going from one media to another?
Because of the change in speed
What does it mean if light bends towards the normal?
It’s slowing down
How does the speed of light change when entering a less dense object
It speeds up and so refracts away from the normal
When does light not refract upon entering a different medium?
When it’s travelling along the normal
What does it mean when light is A) reflected B)refracted C) absorbed B) transmitted
A) the wave bounces off
B) the wave passes into the new material but changes the direction its travelling
C) the wave passes through the material and isn’t absorbed/reflected
D) the wave’s energy is transferred to the material
Why can a prism split up visible light?
Because each colour changes speed by different amounts when they go from a more dense medium to a less dense one (or vice versa)
What is an echo?
When a sound wave is reflected by a hard surface
What is the human range of hearing?
20 -20 000 Hz
What’s ultrasound?
Any sound above 20,000Hz
How does a sound wave affect a solid?
It changes the pressure in the surface causing the particles to vibrate
What kind of waves can vibrations in a solid be passed on as?
Both transverse and longitudinal waves
What determines how vibrations of different frequencies affect a solid?
The shape and properties if a solid
What are the steps to how sound waves travel through the ear?
- Waves enter ear canal
- Sound waves cause the ear drum to vibrate
- Vibrations get passed into tiny bones
- Vibrations pass onto the liquid of the
cochlea - Tiny hairs in the cochlea detect
vibrations forming impulses - Impulses travel along the auditory neurone to reach the brain
What do the small bones in your ear do to the vibrations that came from the ear drum?
They amplify them
What is the thickness of the membrane in the cochlea like?
Thicker and stiffer at the base,
Thinner at the apex
What kind of frequencies do the base and apex of the cochlea detect?
Base detects high frequencies, apex detects lower ones
What do the hair cells in the cochlea do?
Send impulses to the brain as they are connected to a neurone
What’s sonar used for, how does sonar equipment work?
Where ships/submarines use ultrasound to find the depth of the sea or detect fish
- loudspeaker emits ultrasound pulse which spreads through the water
- some gets reflected by the sea bed or fish
- a microphone detects echo and sonar equipment measures the time
How is ultrasound used in getting detailed pictures of unborn babies
Watery jelly is used
A probe is then used to emit and receive ultrasound waves
Ultrasound machine detects time between sending the pulse and receiving g the echo
Why is a watery jelly used in ultrasound?
As it’s a conductive medium enabling a tight bond between skin and probe and allowing ultrasound waves to transmit directly to tissue beneath so less energy is reflected back
Why do ultrasound scans work in producing a picture of a foetus?
Because some of the sound is reflected back when passing into a different medium like fat or bones
What is infrasound?
Sound with a frequency less than 20Hz
What’s the difference between infrasound and ultrasound?
Infrasound travels further than higher frequency waves before they become too faint to detect
What waves are released by earthquakes?
P waves and S waves
What are the properties of P waves?
- longitudinal
- go through a solid, liquid and gas
- this means they can travel through the earth’s layers
What are the properties of S waves?
- transverse
- only can travel through solids
- slower than p waves
- can’t go through the earth as it has a liquid outer core
How do scientists model paths waves have taken through the earth?
By using info about the time waves arrive in different places and speed of waves in different rocks
explain the S wave shadow zone
Takes up large areas of the earth’s as the outer core is liquid
When can P waves have shadow zones and why?
When the waves are refracted as p waves travel faster in solids than liquids meaning P waves slow down upon entering the liquid outer core
What equipment is used to detect seismic waves?
Seismometers
