⭐️Topic SP4 - Waves Flashcards by Meriam nesnas

What are transverse waves?

Waves where the particles move up and down at right angle to wave direction

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Give some examples of transverse waves

Water waves, S waves and em waves

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What are longitudinal waves?

Where particles in the material move parallel to the direction of wave travel

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Give examples of longitudinal waves

Sound waves, p waves

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What’s a difference between transverse and longitudinal waves?

Transverse waves don’t need a medium to travel through but longitudinal waves do

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What is the wave frequency and it’s unit?

The number of waves passing a point each second in Hz

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What does frequency determine for sound and light?

In sound, it determines the pitch and light it determines the colour

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What is the period?

The length of time taken for wave to pass a given point

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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

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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

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What is velocity of a wave?

The speed of a wave in the direction its travelling.

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How do you calculate wave speed using distance and time?

Speed (m/s) = distance (m) / time (s)

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How do you calculate wave speed in terms of frequency and wavelength?

Wave speed (m/s) = frequency (Hz) x wavelength (m)

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Where does refraction of a light ray occur?

At the interface between the two mediums

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When light from air to glass or water,

It refracts towards the normal

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When light goes from a more dense medium to a less dense one,

It refracts away from the normal

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Why does light refract when going from one media to another?

Because of the change in speed

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What does it mean if light bends towards the normal?

It’s slowing down

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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?

1. Waves enter ear canal 2. Sound waves cause the ear drum to vibrate 3. Vibrations get passed into tiny bones 4. Vibrations pass onto the liquid of the cochlea 5. Tiny hairs in the cochlea detect vibrations forming impulses 6. 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