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Physics > Unit 4 - Waves > Flashcards

Unit 4 - Waves Flashcards

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1
Q

What frequency is too low for the human ear to detect?

A

20Hz

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2
Q

What are sounds too low for the human ear to detect called?

A

Infrasounds

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3
Q

Which can travel further: infrasounds or ultrasounds?

A

Infrasounds

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4
Q

Give an animal that can hear infrasounds

A

Elephants

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5
Q

What are seismic waves?

A

Vibrations caused by earthquakes.

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6
Q

What waves do earthquakes and volcanoes create?

A

Infrasounds and sounds we can hear

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7
Q

What is a seismometer?

A

A piece of equipment used to detect seismic waves

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8
Q

What 2 types of waves are seismic waves

A

Longitudinal (P waves)

Transverse (S waves)

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9
Q

What can longitudinal waves be transmitted through

A

Solids, liquids and gases

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10
Q

What can transverse waves that need a medium to travel through be transmitted by

A

Only solids

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11
Q

Name for main parts of the Earth

A

Crust, mantle, outer core (liquid), inner core (solid)

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12
Q

What information do you scientists use to model the paths the waves have taken through the Earth

A

The time the waves arrive in different places and the speed of the waves in different types of rocks

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13
Q

What are shadow zones

A

When S waves or P waves are not detected on the other side of the Earth to the earthquake

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14
Q

How is and S-wave shadow zone formed

A

S waves refract as they passed through the Earth however when some S waves reach the liquid core they cannot be transmitted through it and the waves are absorbed leaving the other side without waves

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15
Q

How are P-wave shadow zones formed

A

This is a band around the Earth. Most waves would be reflected as they pass through the Earth however some are refracted differently when they reach the liquid core. This leaves a larger gap or band between the normal waves and the ones through the liquid core.

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16
Q

Why might weak P-waves arrive in the P-wave shadow zone

A

If waves in the liquid core have been refracted by something solid

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17
Q

What is the highest frequency that human ears can detect

A

20,000 Hz

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18
Q

What is ultrasound

A

Sounds made by Waze with higher frequencies than 20,000 Hz

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19
Q

What do dolphins and bats use ultrasound for

A

To detect objects around them

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20
Q

What is Sonar

A

Equipment carried on ships or submarines that uses ultrasound to find the depth of the sea or to detect fish

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21
Q

How does Sonar work

A

A loudspeaker on the ship emits a pulse of ultrasound which spreads through the water. Some of it is reflected by the seabed. A special microphone on the ship detects the echo and the sonar equipment measures the time between the sound sent and the echo returning.

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22
Q

Apart from detecting, what can ultrasound be used for

A

To make images of things inside the body such as unborn babies

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23
Q

How does an ultrasound scan work

A

A gel is used to stop the ultrasound just reflecting from the skin. The probe emits and receives ultrasound scans. Some sound is reflected when the ultrasound waves pass into a different medium such as fat or bone. The ultrasound machine detects the time between sending the pulse and receiving the echo and the display shows where the echoes confirm which creates the image.

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24
Q

What waves are soundwaves

A

Longitudinal waves

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25
Q

What happens to the particles in a longitudinal wave

A

The particles in a gas or liquid vibrate backwards and forwards as the soundwave passes but when they reach a solid some energy is reflected as some is transmitted or absorbed

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26
Q

What does a soundwave cause on the surface of a solid

A

Changes in pressure which causes particles in the solid to vibrate. The disturbance is passed from the Earth with the solid. The vibrations in the solid can be passed on both as longitudinal waves and transverse waves

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27
Q

What determines how vibrations of different frequencies affect solids

A

The shapes and properties such as density and stiffness

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28
Q

Give the stages of how we hear things

A

Soundwaves enter the ear canal.
Soundwaves make the eardrum vibrate (a thin membrane)
Vibrations are passed on to tiny bones which amplify them
Vibrations are passed on to the liquid inside the cochlea
Tiny hairs in the cochlear detect the vibrations and create electrical signals called impulses.
Impulses travel along neurones in the auditory nerve to reach the brain

29
Q

Approximately how big is the cochlea

A

9 mm

30
Q

What is the cochlea

A

A coiled tube containing a liquid

31
Q

What range of sounds can the human ear detect

A

From 20 Hz to 20,000 Hz

32
Q

Describe the cochlea if it was unwound

A

The base is at the start and is thicker and detects high frequencies
The membrane contains the hair cells
The apex is at the end and is thinner and detects low frequencies

33
Q

What makes different parts of the membrane vibrate

A

The frequency of the soundwave is in the liquid inside the cochlea as different thicknesses of the membrane vibrate best at different frequencies

34
Q

What is the purpose of the tiny hairs

A

They detect the vibrations and each is connected to a neurone that sends impulses to the brain

35
Q

What four things can happen when a wave reaches an interface

A

Reflected, reflected, transmitted and absorbed

36
Q

Why do some objects appear lighter than others

A

They reflect more light

37
Q

Why do some objects appear darker than others

A

They absorb more light

38
Q

What light is from lightbulbs or the sun

A

White light

39
Q

What are colours

A

Different frequencies of white light

40
Q

Why can a prism be used for split up visible light into the colours of the rainbow

A

Different colours and light change speed by different amounts when they travel from air to glass or vice versa. This means they are refracted through different angles so they are split up

41
Q

How can we hear echoes

A

When sound is reflected by a hard surface

42
Q

Can sound waves be refracted

A

Yes, when it goes into different materials

43
Q

What is wave velocity equal to

A

The frequency multiplied by the wavelength

44
Q

When does the frequency of a soundwave change

A

When we hear sounds of different pitches

45
Q

When does the wavelength or velocity of a soundwave change

A

If the sound has a same pitch and we hear it through a different material

46
Q

What happens to like travelling along the normal when it goes into a different medium

A

There is no change in direction

47
Q

Why do objects of the bottom of a swimming pool look closer than it really is

A

Light reflected by it changes direction when it leaves the water

48
Q

What affects the bend of the light

A

How fast the light travels in the two media and the angle of the light hitting the interface

49
Q

What will make the light bend more

A

If the difference in speed is greater between the two media

50
Q

What direction does the light bend when it slows down

A

Towards the normal

51
Q

What waves can we use to help us understand what happens when light waves

A

Waterwaves

52
Q

What affects the speed of water waves?

A

The depth of the water

53
Q

What will happen to waves from deep to shallow?

A

They will slow down and change direction - towards the normal

54
Q

Why is it impossible to take pictures of things that are deep down in the seabed

A

Light waves don’t travel very far in seawater as they are either absorbed or reflected by tiny particles in the water

55
Q

Explain the core practical - investigating waves on water

A

Set up a ripple tank with a straight dipper at one end of the tank and fasten a ruler to one of the adjacent sides above water level
Very the voltage to the motor until you can only see two ways along the ripple tank
Count the waves formed in 10 seconds and write it down
Use the ruler to estimate the wavelength and calculate the speed using the length and the frequency
Mark two points on the ruler and measure the distance and use the stopwatch to find the time it takes for a wave to go from one mark to this information to calculate the speed.

56
Q

Explain the core practical – investigating waves in solids

A

Suspend a metal rod horizontally using a clamp and rubber bands
Hit one end with a hammer. Hold a smart phone with a frequency at near the rod and note down the peak frequency
Measure the length of the road and the wavelength will be twice the length of the rod
Use the frequency and wavelength to calculate the speed of sound in the rod

57
Q

What is the equation for wave speed

A

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

58
Q

What is the speed of light in a vacuum

A

300,000,000 m/s

59
Q

Describe a way of measuring the speed of waves on water

A

Measuring the time it takes for a wave to travel between two fixed points such as buoys. The speaker can be calculated from the time and distance

60
Q

What waves are water waves

A

Transverse

61
Q

How is energy transferred in waterwaves

A

Particles in the water move up and down as a wave passes – they are not carried to the shore

62
Q

What waves our sound waves

A

Longitudinal

63
Q

How is energy transferred in longitudinal waves

A

Particles in the material move backwards and forwards as the wave passes in the same direction the wave is travelling

64
Q

What ways do not need a medium to travel through

A

Electromagnetic waves

65
Q

For soundwaves, what does the frequency determine

A

The pitch

66
Q

What is the period

A

The length of time it takes one wave to pass a given point

67
Q

What is the ampliture

A

Maximum distance of a point on a wave from its rest position in metres

68
Q

What does the amplitude determine

A

How loud the sound is

Physics (12 decks)

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