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Physics IGCSE > Unit 3 - Waves > Flashcards

Unit 3 - Waves Flashcards

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1
Q

Source of waves

A

Produced by vibrations causing a disturbance which spreads out from the source

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2
Q

What waves transfer

A

Waves transfer energy from one place to another without transferring matter

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3
Q

Types of waves

A
  • Transverse wave
  • Longitudinal wave
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4
Q

Transverse wave

A

The particles oscillate perpendicular to the direction of propagation of the wave

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5
Q

Longitudinal wave

A

The particles oscillate parallel to the direction of propagation of the wave

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6
Q

Crest

A

The peak of the wave

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7
Q

Trough

A

The lowest point of the wave

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8
Q

Amplitude

A

The height of the wave

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9
Q

Frequency

A

The number of complete waves that pass a point each second

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10
Q

Unit of frequency

A

Hertz (Hz)

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11
Q

Wavelength

A

The distance between one wave crest and the next (or trough)

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12
Q

Wave speed calculation

A

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

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13
Q

Relationship with amplitude and energy

A

If amplitude increases, more energy is transferred per second

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14
Q

Transverse wave examples

A
  • Ripples along the surface of water
  • Waves formed by shaken rope
  • Visible light and electromagnetic radiation
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15
Q

Longitudinal wave examples

A
  • Waves produced when ends of a stretched spring are moved
  • Sound waves- series of compressions and rarefactions
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16
Q

Earthquake waves

A
  • Primary waves - longitudinal - ground is compressed in the same direction as the wave travels
  • Secondary waves - transverse - ground rises and falls as wave passes through
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17
Q

Reflection

A

When a wave ‘bounces’ off a boundary

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18
Q

Refraction

A

When a wave moves from one medium to another and changes speed and hence direction

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19
Q

Diffraction

A

When a wave spreads as it moves through a gap or passes and edge

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20
Q

Incident wave

A

The wave before it reaches a boundary

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21
Q

Reflected wave

A

The wave after it has hit the boundary and bounced off

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22
Q

Reflection constants

A
  • Wave speed, frequency and wavelength doesn’t change
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23
Q

Increasing effect of diffraction

A

Gap and wavelength are of similar size

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24
Q

Normal line

A

Drawn to measure angle of incidence and reflection

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25
Q

Law of reflection

A

Angle of incidence = Angle of reflection

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26
Q

Virtual image

A

When rays of not pass through the place an image is seen - hence can’t be projected onto screens

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27
Q

Real image

A

An image that can be projected onto a screen because the rays of light actually pass through the position of the image

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28
Q

Refractive index

A

Shows how much the speed of light changes when it moves from a vacuum to a certain material

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29
Q

Refractive index equation

A

Refractive index (n) = Speed of light in vacuum ÷ Speed of light in a substance

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30
Q

Snell’s law

A

Relationship with angle of incidence and refraction is constant ration which is refractive index
n = sin i ÷ sin r

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31
Q

Light reflecting off the back surface of a medium

A

Internal reflection

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32
Q

Total internal reflection

A

When all of the light leaving a glass block is reflected back inside

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33
Q

Needs for total internal reflection

A
  • Angle of incidence if greater than critical angle
  • Wave needs to speed up after it passes across
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34
Q

Critical angle

A

The largest angle of incidence which allows light to escape the medium

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35
Q

Relationship of critical angle and refractive index

A

refractive index (n) = 1 ÷ sin c

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36
Q

Use of total internal reflection

A

Optical fibers - transmis optical pulses over long distances, pulse can be detected since the pulse doesn’t leave the fibre
- Optical fibers - endoscopes

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37
Q

Types of actions of lenses

A
  • Diverging light (spreading it out)
  • Converging light (bringing it towards a point)
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38
Q

Converging lens

A
  • Refracts light rays to come together
  • If light rays are parallel to each other and to the optical axis, rays will come together to the principal focus
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39
Q

Optical axis

A

The line which passes through the centre of the lens

40
Q

Principal focus

A

The point where the rays of light in a converging lens are brought together

41
Q

Focal length

A

The distance between the centre of the lens and the principal focus

42
Q

Characteristics of an image with a converging lens

A
  • Enlarged or diminished
  • Upright or inverted
  • real or virtual
43
Q

Type of image with a converging lens and an object inside the focal length

A

An upright, magnified, virtual image

44
Q

Type of image with converging lens and an object twice the focal length

A

An inverted, diminished, real image

45
Q

Diverging lens

A
  • Refracts rays of light to spread apart
  • if light rays are parallel to each other and optical axis, they will be spread out from the same place - the principal focus of the lens
46
Q

Relationship of focal length and lens strength

A

The shorter the focal length, the more powerful the lens

47
Q

Properties of an image with a diverging sense

A
  • Virtual - rays do not pass through
  • Diminished - always is smaller than the original
  • Upright - same way up as the original object
48
Q

Converging lenses in the eye

A
  • Cornea
  • Lens
  • Both focus light onto the retina
49
Q

Far point vs. near point

A
  • Far point - most distant point you can focus your eye to
  • Near point - closest point you can focus on
50
Q

Short-sightedness

A
  • Thick lens causes light from distant objects to be focused in front of the retina, far point decreases
51
Q

Long-sightedness

A
  • Lens isn’t thick enough or eyeball is to short causes light from nearby objects to be focused on a point behind the retina, near point increases
52
Q

Dispersion

A

When a ray passes through a medium and splits the white light splits into different components/wavelengths

53
Q

Seven colors of white light in dispersion in increasing frequency

A
  • Red
  • Orange
  • Yellow
  • Green
  • Blue
  • Indigo
  • Violet
54
Q

Light of only a single frequency

A

Monochromatic

55
Q

Electromagnetic waves, wave type

A
  • Transverse waves
56
Q

Special feature of electromagnetic waves

A
  • Can travel in a vacuum
57
Q

Electromagnetic waves from shortest to largest

A
  • Gamma rays
  • X-ray
  • Ultra-violet
  • Infrared
  • Micro-waves
    -Radio waves
58
Q

Non-ionizing radiation

A

Type of radiation that does not directly damage cells unless intense

59
Q

Ionizing radiation

A

Radiation that can damage cells even at low intensity

60
Q

Reasons for different wavelengths

A

Electrons that oscillate at different frequencies

61
Q

How radio and television broadcasts work

A

Radio signals are refracted by upper atmosphere and can travel past the curvature of earth

62
Q

Radio astronomy

A

Using large radio waves to detect weak radii signals from stars and black holes

63
Q

Uses of microwaves

A
  • Microwave ovens - cooks food by heating rapidly
  • Satellite and phone communication - microwaves can penetrate upper atmosphere, can be used with low power in mobile phone networks
64
Q

Danger of microwaves

A
  • Heating effect damages living tissue
65
Q

Uses of infrared radiation

A
  • Remote controls - uses pulses of infrared to be detected on television
  • Cooking - heating effect when absorbed is used for cooking
  • Thermal imaging and alarms - night vision, identifying energy loss, finding hotspots, medical diagnosis
  • Communication - used in fibre optic networks
66
Q

Dangers of infrared radiation

A

Heating effect that can bun skin

67
Q

Visible light

A

Electromagnetic radiation that can be seen by the eye

68
Q

Ultraviolet radiation

A

Produced by the sun and absorbed by the atmosphere

69
Q

Uses of ultraviolet radiation

A
  • Biological washing powder
  • Bleaching paper exposed to UV
  • Sterilizes water in waste treatment plants and water supplies - kills microbes
70
Q

Danger of UV

A

Damaging to skin and eyes - ca burn skin cells and lead to cancer

71
Q

X-rays

A

Short wavelength electromagnetic waves - produce fast-moving electrons
- Also emitted by stars and astronomical objects

72
Q

Uses of X-rays

A
  • X-ray machines to take photos of bones inside the body since rays go through bones and muscle easily - can be used by doctors
  • Security in airports and more - luggages can be scanned for dangerous objects
73
Q

Danger of X-rays

A

Can damage cells - especially growing ones

74
Q

Gamma rays

A

Produced by the radioactive decay of a nucleus

75
Q

Uses of gamma rays

A
  • Gamma camera - used to show how healthy organs are if radiation is emitted
  • Radiotherapy - kills cancerous cells
  • Sterilize medical equipment
76
Q

Dangers of gamma rays

A

Damages DNA inside cells which can cause cancer

77
Q

Two most important types of satellites

A
  • Low Earth Orbit (LEO) satellites - not far above the atmosphere moving quickly across the sky
  • Geostationary satellite - far out in an orbit that makes them seem stationary
78
Q

Low Earth Orbit satellites

A
  • Some used for spying or observing weather
  • Part of phone networks or internet
79
Q

Geostationary satellites

A
  • Positioned 36000km above the Earth’s equator
  • Takes exactly one day to orbit the planet
  • Used for satellite television
  • Some used for phone networks
80
Q

Optical fibres

A
  • Use visible light or infrared radiation to transmit large amounts of information very quickly
81
Q

Speed of a pulse calculation

A

Speed = speed in vacuum ÷ refractive index

82
Q

Analog signal

A

The signal can be any level within a range and varies continuously

83
Q

Digital signal

A

The signal has fixed levels - often two; called 0 & 1 - information is sent in poses of fixed duration

84
Q

Signal regeneration

A

Removes most of the noise and distortion from the transmission of a signal

85
Q

Medium

A

The material through which a wave passes

86
Q

Effect of having larger vibrations on sound

A
  • Increased amplitude = increased volume
87
Q

Effect of having faster vibrations on sound

A
  • Increased frequency = Increased pitch
88
Q

Wave type of a sound wave

A

Longitudinal wave - particles travel parallel to wave propagation

88
Q

Compressions

A

A region of air where the particles are closer together than normal due to a sound wave passing through it

89
Q

Rarefactions

A

A region of air where the particles are further apart than normal due to a sound wave passing through it

90
Q

Direction of movement of compressions and rarefactions

A

Away from the source of the sound in all directions - spreading the sound wave outwards

91
Q

Echo

A

The reflection of a sound wave after hitting a hard surface

92
Q

Speed of sound in different media

A
  • Air - 343m/s
  • Helium gas - 972m/s
  • Water - 1500m/s
  • Mercury - 1450m/s
  • Gold - 3240m/s
  • Iron - 5130m/s
  • Glass - 5640m/s
  • Diamond - 12000m/s
93
Q

Speed of sound in a vacuum

A

Sound doesn’t travel in a vacuum because there are no particles to transfer vibrations

94
Q

Frequency range that the human ear can detect

A

20-20000Hz

95
Q

Ultrasound

A

Sound waves with a frequency above 20000Hz

96
Q

Uses of ultrasound

A
  • Measure distances using echoes
  • Sonar - e.g. measuring depth of the ocean
  • Checking for damage in materials - ultrasonic pulse would detect echoes if cracks are present
  • Medical scanning

Physics IGCSE (6 decks)

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