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Physics 9-1 iGCSE Oxford AQA > Waves > Flashcards

Waves Flashcards

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1
Q

What is a wave?

A

Disturbance caused by oscillating source that transfers energy & info in the direction of wave travel, without transferring matter

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2
Q

What is amplitude?

A

Wave’s maximum disturbance from its undisturbed position

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3
Q

Illustrate amplitude on a wave

A
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4
Q

What is wavelength?

A

Distance between the same point on two adjacent waves

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5
Q

Illustrate wavelength on a wave

A
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6
Q

What is frequency?

A

Number of complete waves passing a certain point per second

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7
Q

What is frequency measured in?

A

Measured in hertz (Hz)

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8
Q

What does 1 Hz mean?

A

1 Hz is 1 wave per second

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9
Q

In transverse waves, what are oscillations (vibrations) like?

A

Oscillations (vibrations) are perpendicular (at 90°) to direction of energy transfer

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10
Q

Give 3 examples of waves that are transverse

A
  • All electromagnetic waves e.g. Light
  • Ripples and waves in water
  • A wave on a string
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11
Q

In longitudinal waves, what are oscillations (vibrations) like?

A

Oscillations are parallel to the direction of energy transfer

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12
Q

Give 2 examples of longitudinal waves

A
  • Sound waves in air e.g. Ultrasound
  • Shock waves e.g. Some seismic waves
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13
Q

Longitudinal waves have areas of ______ and ______

A

Compression and rarefraction

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14
Q

Sound waves are _______ and ________ waves

A

longitudinal and mechanical waves

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15
Q

What is wave speed?

A

The speed at which energy is being transferred (or speed wave is moving at)

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16
Q

All waves can be ______, ______ or ______ at the boundary between two different materials

A

Absorbed, Transmitted or Reflected

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17
Q

When waves are absorbed by material, what happens (energy wise)?

A

Energy is transferred into material’s energy store (e.g. How microwaves work)

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18
Q

What is meant when waves are transmitted?

A

Waves carry on travelling through new material - often leads to refraction

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19
Q

What is a period of a wave?

A

Amount of time it takes for a full cycle of the wave to pass a point

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20
Q

What is a wave front?

A

Is the locus of points in the same phase

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21
Q

Why can waves undergo refraction?

A

Due to a change in wavelength

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22
Q

What is the rule for all reflected waves?

A

Angle of incidence = Angle of reflection

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23
Q

What is the angle of incidence?

A

Angle between incoming wave and the normal

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24
Q

What is the angle of reflection?

A

Angle between reflected wave and the normal

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25
Q

What is the normal?

A

An imaginary line that’s perpendicular to the surface at the point of incidence (point where wave hits boundary)

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26
Q

When is a wave refracted?

A

When wave crosses boundary between materials at an angle, it changes direction

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27
Q

How much a wave refracts depends on…

A
  • How much the wave speeds up or slows down
  • Which depends on density of two materials
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28
Q

The higher density of material = _____ wave travels through it

A

slower

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29
Q

When wave crosses a boundary and slows down, it bends _____ the normal

A

Slow = TOWARDS the normal

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30
Q

When wave crosses a boundary and speeds up, it bends _____ ___ the normal

A

fast = AWAY from the normal

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31
Q

What changes when a wave refracts?

A

Wavelength of wave

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32
Q

What stays the same when a wave refracts?

A

Frequency stays the same

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33
Q

What will happen if a wave travels along the normal?

A

It will change speed but NOT be refracted

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34
Q

What is the optical density of material?

A

A measure of how quickly light can travel through it

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35
Q

Higher optical density = ….

A

slower light waves travel through it

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36
Q

Describe how you can construct a ray diagram to show refraction with an aid of a diagram

A
  1. Draw boundary line & normal (90° to boundary)
  2. Draw incident ray that meets normal at boundary + angle of incidence
  3. Draw refracted ray on other side of boundary
    1. If 2nd material is more opictially dense than 1st = angle of refraction < angle of incidence
    2. If 2nd material is less opictially dense than 1st = angle of refraction > angle of incidence
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37
Q

What is diffraction?

A

Spreading of waves when they pass through (narrow) gap or move past (edge of) obstacle

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38
Q

When does diffraction take place?

A

When wavelength of wave is comparable to size of obstacle or gap

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39
Q

Waves passing through gap/past edge of obstacle spread out without changing their… (name 3 things)

A
  • Wavelength
  • Speed
  • Frequency
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40
Q

Wider gap = …

A

less waves spread out (the smaller the diffraction)

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41
Q

Narrower gap = …

A

more the waves spread out (the greater the diffraction)

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42
Q

Illustrate diffraction of waves through a wide gap

A
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43
Q

Illustrate diffraction of waves through a narrow gap

A
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44
Q

Illustrate diffraction of waves at an edge

A
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45
Q

Name 3 real life examples of where diffraction is used

A
  • Optical instruments
  • Ultrasound waves in medicine
  • Radio wave reception
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46
Q

Explain how ultrasound waves in medicine work

A

Spread out from hand-held transmitter & reflect from tissue
boundaries inside womb

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47
Q

What happens if the transmitter is too narrow?

A

Waves spread out too much = image becomes too faint

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48
Q

What are narrow telescopes for?

A

Closer stuff

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49
Q

Explain how diffraction is used in the Hubble Space Telescope

A
  1. Small amount of light passes through Hubble Space Telescope = small amount of diffraction occurs
  2. Because telescope is so wide
  3. Images are clear and detailed
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50
Q

Why do people who in hilly areas have poor TV reception?

A

Radio waves passing top of hill are diffracted by hill but they don’t spread enough behind the toll

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51
Q

What are electromagnetic waves?

A

Transverse waves → transfer energy from a source to an absorber

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52
Q

All EM waves travel at the ____ ______ through ___ or _____

A

Travel at the same speed through air or vacuum (space)

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53
Q

EM waves form _____ _______ over a range of _________

A

continuous spectrum over a range of frequencies

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54
Q

How are EM waves grouped? (3x)

A

Based on their wavelength, frequency and energy

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55
Q

Recite the order of EM waves within the spectrum (from low freq. to high freq.)

A
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56
Q

What do the wavelengths of the electromagnetic spectrum range from?

A

10-15 m to 104 m and beyond

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57
Q

Why is there such a large range of frequencies of EM waves?

A

Because EM waves are generated by a variety of charges in atoms and their nuclei

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58
Q

Shorter wavelength = ….

A

higher its frequency = higher the energy

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59
Q

How is visible light detected?

A

By our eyes

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60
Q

How do we see the different wavelengths of visible light as?

A

As different colours

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61
Q

What 4 EM waves are used for communication?

A
  • Radio waves
  • Microwaves
  • Infrared
  • Visible Light
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62
Q

What are radio waves?

A

EM radiation - wavelength longer than 10 cm

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63
Q

Why can long-wave radio waves (1-10 km) be transmitted from e.g. London to halfway round world?

A

Because long wavelengths diffract (bend) around curved Earth surface i.e. they can diffract around hills, into tunnels, etc.

∴ Radio signals can be received even if receiver isn’t in line of
the sight of transmitter

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64
Q

Why can short-wave radio signals (10m-100m) be received long
distances from a transmitter?

A

Because they’re reflected from the ionosphere

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65
Q

How does Bluetooth work?

A

Uses short-wave radio waves to send data over short distance between devices without wires

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66
Q

Medium-wave signals (shorter ones) can relate from ionosphere depending on _______ ________ and ____ of day

A

depending on atmospheric conditions and time of day

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67
Q

What kind of wavelength do radio waves that are used for TV and FM radio transmissions have?

A

Very short wavelengths

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68
Q

To get reception why must TV and FM radio transmissions signals be in direct sight of the transmitter?

A

Signal doesn’t bend or travel far though buildings

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69
Q

Name 3 uses of radio waves

A
  • TV
  • Radio Systems
  • Bluetooth
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70
Q

Name 2 uses of microwaves

A
  • Mobile phones
  • Satellite television systems
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71
Q

Why does communication to and from satellites use microwaves?

A

They can easily pass through earth’s watery atmosphere

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72
Q

Why is there a slight time delay between signal being sent and received?

A

∵ of long distance signal has to travel

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73
Q

Why are microwaves used to beam signals from one place to another and not radio waves?

A

∵ they don’t spread as much as radio waves

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74
Q

Name 3 uses of infrared

A
  • TV remote controls
  • Night vision devices
  • Heating
75
Q

What does absorbing IR radiation cause objects to get?

A

Hotter

76
Q

How can food can be cooked using IR radiation?

A

Temperature of food increases when it absorbs IR radiation

77
Q

What does every object do (regarding IR radiation)?

A

They absorb and emit infrared radiation

78
Q

Why do all objects emit IR radiation?

A

∵ of motion of their particles

79
Q

Hotter object is = more …

A

IR it radiates in given time

80
Q

What does the amount and frequency of emitted raditation depend on?

A

Temperature and surface of object

81
Q

What do objects at constant temperature do?

A

Emit IR radiation at same rate that they absorb it

82
Q

What does an object that’s hotter than its surroundings do?

A

Emits more IR radiation > than it absorbs as it cools down

83
Q

What does an object that’s cooler than its surroundings do?

A

Absorbs more IR radiation > than it emits as it warms up

84
Q

Dark, matt surfaces are ___ ____ and ___ ____ of infrared radiation

A

good absorbers and good emitters

85
Q

Light, shiny surfaces are ____ ______ and ___ _____ of infrared radiation

A

poor absorbers and poor emitters

86
Q

Light, shiny surfaces are ___ _______ of infrared radiation

A

good reflectors

87
Q

As an object heats up, what does it do?

A

Radiates more infrared radiation, at higher frequencies

88
Q

What is black-body radiation?

A

Range of electromagnetic radiation emitted by an object at a particular temperature

89
Q

What is a perfect black body?

A

Object that absorbs all of radiation that hits it, no radiation is transmitted or reflected

90
Q

What happens if the atmosphere absorbs more radiation without emitting same amount?

A

Overall temperature will rise until absorption and emission are equal (global warming)

91
Q

Name 2 uses of visible light

A
  • Fibre optic communications
  • Photography
92
Q

What are optic fibres?

A

Thin glass or plastic fibres that carry data over long distances as pulses of visible light

93
Q

How do fibre optic cables use visible light to transmit data?

A
  • Work because of reflection → light rays are bounced back and forth until they reach end of fibre
  • Light is not easily absorbed or scattered as it travels along fibre
94
Q

Name 2 uses of UV

A
  • Security pens
  • Artificial tans
95
Q

How does security marking work?

A
  • Security pens → mark property with name
  • Under UV light ink will glow (fluoresce) but it’s invisible otherwise
  • Helps police identify your property if it’s stolen
96
Q

What are X-rays used for?

A

Medical imaging - to see if a person has broken bones

97
Q

How do X-rays work?

A
  • X-rays transmit easily through flesh but very easily through denser material like bones/metal
  • Starts off as white
    • White = x-rays absorbed
    • Black = x-rays transmitted
98
Q

Name 2 uses of gamma rays

A
  • Sterilising surgical instruments
  • Killing harmful bacteria in food
99
Q

What is the problem with low energy waves?

A

Have a heating effect

100
Q

What is the problem with high energy waves?

A

Have enough energy to cause ionisation

101
Q

What is the danger of microwaves?

A

Heating of body tissue

102
Q

What is the danger of infrared?

A

Skin burns

103
Q

What are the dangers of ultraviolet? Name 2

A

Skin cancer and blindness

104
Q

What is the danger of X-rays?

A

High doses kill cells

105
Q

What is the danger of gamma rays?

A

Genetic mutations

106
Q

What radiographers do to protect themselves from the effects of gamma rays/x-rays?

A
107
Q

X-rays affect a photographic lm in the same way as ____

A

light

108
Q

Name 4 things X-rays are used in

A
  • CT scanning
  • Bone fractures
  • Dental problems
  • Killing cancer cells
109
Q

How can X-rays and gamma rays be used to treat people with cancer?

A

∵ high doses of these rays kill all living cells → they’re carefully directed towards cancer cell

110
Q

Why is gamma radiation used as medical tracer?

A

Can pass out through body to be detected

111
Q

What are sound waves?

A

Longitudinal waves and cause vibrations in medium, which are detected as sound

112
Q

Why can’t sound waves travel in space?

A

There’s no particles to move/vibrate

113
Q

What is the range of human hearing?

A

20 Hz to 20 000 Hz

114
Q

How is the pitch of sound determined?

A

By frequency of vibrations of source

115
Q

How is the loudness of sound determined?

A

Size of amplitude of disturbance

116
Q

Sounds can ____, _____ & ____

A

Reflect, refract and diffract

117
Q

What reflects sound waves?

A

Hard flat surfaces

118
Q

What are echoes essentially?

A

Reflected sound waves

119
Q

What is ultrasound?

A

Ultrasound is a sound with frequencies higher than 20 000 Hz

120
Q

Explain how electronic systems can be used to produce ultrasound

A
  1. Electrical devices can produce electrical oscillations of any frequency
  2. Then conserved into mechanical vibrations to produce sound waves beyond range of human hearing
121
Q

Ultrasound waves get ____ _______ at boundaries between two different media

A

partially reflected

122
Q

What is meant by partial reflection?

A

When wave passes from 1 medium into another:

  • Some of wave reflected off boundary
  • & some is transmitted (and refracted)
123
Q

How can we use the partial reflection in ultrasound?

A

Time taken for reflections to reach a detector can be used to measure how far away boundary is

124
Q

Name 3 uses of ultrasound

A
  • Prenatal scanning
  • Removal of kidney stones
  • Finding flaws in objects (like pipes or materials)
125
Q

Explain how ultrasound can be used in prenatal scanning

A
  1. Ultrasound waves → pass through body but when reach boundary between two different media (e.g. fluid in womb and skin of foetus) = some of wave reflected back & detected
  2. Exact timing + distribution of these echoes → processed by computer
    • → produces video image of foetus
126
Q

Explain how ultrasound can be used in finding flaws in objects like pipes or materials

A
  1. Ultrasound waves entering material → reflected by far side of material
  2. If there’s flaw (e.g. Crack inside object) = wave will be reflected sooner
127
Q

What can CT scans do?

A

Distinguish between different types of soft tissue as well as between bone and soft tissue

128
Q

Explain how CT scans work

A
  1. Take range of X-ray images from various position
  2. → processed by computer to build 3D image of inside of patient’s body
129
Q

Name 3 pros of CT scans

A
  1. Lets doctor gain much greater insight into what’s wrong with patient
    1. Only method that provides detailed images of bone, soft tissue, blood vessels
  2. Painless
  3. Widely available
130
Q

Name 3 cons of CT scans

A
  1. Exposure to radiation
  2. Allergic reaction to contrast material
  3. Misinterpreted test results
131
Q

How can you can measure risk of radiation?

A

Using Radiation Dose in Sieverts

132
Q

What does risk depend on?

A

Total amount of radiation absorbed and how harmful the type of radiation is

133
Q

How is ultrasound used remove kidney stones?

A
  1. Powerful ultrasound waves used to break kidney stone into bits
  2. Fragments are then small enough to leave kidney naturally
134
Q

When something moves towards you, what happens to the wavelength and frequency of sound?

A

Wavelength decreases and frequency increases

135
Q

When something moves towards you, what happens to the pitch of sound?

A

Becomes higher

136
Q

When something moves away from you, what happens to the wavelength and frequency of sound?

A

Wavelength increases and frequency decreases

137
Q

When something moves away from you, what happens to the pitch of sound?

A

Becomes lower

138
Q

What an image produced in a plane mirror like? (name 3 things)

A
  • Virtual
  • Upright
  • Laterally inverted
139
Q

What can the refraction by a prism lead to? (2x)

A

Dispersion of light waves and formation of a spectrum

140
Q

When does total internal reflection occur?

A

Angle of incidence in denser medium > critical angle

141
Q

How is visible light and infrared transmitted through optical fibre via?

A

Total internal reflection

142
Q

What are optical fibres used for? (2x)

A
  • Communication technology
  • Medicine e.g. endoscope
143
Q

What is an endoscope used for?

A

To see inside body cavity without cutting body open

144
Q

Explain how an endoscope works

A
  1. Contains 2 bundles of optical fibres
    1. Used to shine light into cavity
    2. Transmit light back so surgeon can see internal surface of cavity
      • Tiny lens = image at the end of fibres (seen directly or using camera)
145
Q

Name 2 benefits of optical fibres

A
  1. Can carry more info than ordinary cable of same thickness
  2. Signals in optical fibres don’t weaken as much over long distances as signals in ordinary cables
    1. Don’t need to be amplified as often as signals in copper cables
146
Q

How does a lens form an image?

A

By refracting light

147
Q

What happens to light in a convex lens?

A

Bulges outwards - causes rays of light parallel to axis to be brought together (converge) at principal focus

148
Q

What happens to light in a concave lens?

A

Cave inwards - causes rays of light parallel to axis to spread out (diverge)

149
Q

What is the focal length?

A

Distance form centre of lens to principal focus

150
Q

To describe an image properly, what are the 3 things you need to say?

A
  1. How big it is compared to object
  2. Whether it’s upright or inverted (upside down) relative to object
  3. Whether it’s real or virtual
151
Q

What is a real image?

A

Where light from an object comes together to form an image on a ‘screen’ (e.g. eye’s retina)

152
Q

What is a virtual image?

A

When rays are diverging so light from the object appears to be coming from a completely different place

153
Q

Give 2 examples of virtual image

A
  • Image of your face in a mirror
  • Image gottenvwhen looking at an object through a magnifying lens
154
Q

What type of lens do magnifying glasses use?

A

Convex Lenses

155
Q

Object being magnified must be _____ to lens than the ____ length

A

Closer to lens than the focal length

156
Q

What’s a useful pharse to use in exam if they ask you about virtual images?

A

“you can’t project a virtual image onto a screen”

157
Q

Name 7 parts of the eye

A
  • retina
  • variable focus lens
  • cornea
  • pupil
  • iris
  • ciliary muscle
  • suspensory ligaments
158
Q

What is the retina?

A

Light sensitive cells at back of your eye

159
Q

What is the function of the retina?

A

Where lens will focus light rays from object and real image will be formed

160
Q

What’s the function of the variable focus lens?

A

Focuses light into retina

161
Q

What’s the function of the cornea and what is it?

A

Transparent layer that protects eye & helps to focus light into retina

162
Q

What’s the function of the pupil and what is it?

A

Central hole formed by iris - light enter eye through pupil

163
Q

What’s the function of the iris and what is it?

A

Coloured ring of muscle that controls amount of light that can enter eye

164
Q

What is the function of ciliary muscles?

A

Causes changes in shape of lens = allow light to be focused arriving from varying distances

165
Q

What do the suspensory ligaments do?

A

Attach ciliary muscles to the lens

166
Q

Light entering the eye is refracted by what?

A

Cornea & Lens

167
Q

What is usually the near point of a human eye?

A

Approximately 25 cm from the eye

168
Q

What is usually the far point of a human eye?

A

Infinity from the eye

169
Q

What can the eye focus on? (objects between…)

A

Objects between near point and far point

170
Q

What meant by the range of vision?

A

Distance between the near point and far point

171
Q

What is long-sightedness caused by?

A

Eyeball being too short OR eye lens being unable to focus a sharp image on the retina

172
Q

What is short-sightedness caused by?

A

By eyeball being too long OR eye lens being unable to focus a sharp image on the retina

173
Q

Where does long-sightedness cause the image to form?

A

Behind retina

174
Q

Where does short-sightedness cause the image to form?

A

Before retina

175
Q

How can long-sightedness be corrected?

A

By using a convex (convering) lens

176
Q

How does a convex lens correct long-sightedness?

A

Causes light rays to converge slightly before they hit lens = they refract perfectly onto retina

177
Q

How can short-sightedness be corrected?

A

With concave (diverging) lens

178
Q

How does a concave lens correct long-sightedness?

A

Light rays diffract outwards slightly as they pass lens = focused exactly on retina by lens in eye

179
Q

What are lasers?

A

Concentrated sources of light

180
Q

Name 3 uses of lasers

A

Cutting, cauterising and burning

181
Q

Why are lasers used in eye surgery?

A

To correct visual defects

182
Q

In the eye, the image is brought to focus on retina by changing the shape of the lens. What is the camera equivalent?

A

Image is brought to focus on film or CCD sensor by varying the distance between flim and lens

183
Q

What is the camera equivalent of the retina?

A

Film or CCD sensor

Physics 9-1 iGCSE Oxford AQA (12 decks)

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