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AQA GCSE Physics > Waves > Flashcards

Waves Flashcards

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1
Q

What do waves do?

A

Transmit energy not matter

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2
Q

What are the three pairs of words used to classify waves?

A
  • Mechanical/ Electromagnetic
  • Progressive/ Stationary
  • Transverse/Longitudinal
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3
Q

What is a mechanical wave?

A

A wave which requires a medium (particles) through which to transfer energy

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4
Q

What is an electormagnetic wave?

A

A wave which does not require a medium through which to transfer energy

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5
Q

What is a progressive wave?

A

A wave where there is a net transfer of energy from the source to a receiver

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6
Q

What is a stationary wave?

A

A wave where there is no net transfer of energy, the energy is stored in the wave

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7
Q

What is a transverse wave?

A

A wave where the direction of disturbance is perpendicular to the direction of energy transfer

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8
Q

What is a longitudinal wave>

A

A wave where the direction of disturbance is parallel to the direction of energy transfer

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9
Q

What do longitudinal waves consist of?

A

Compressions and rarefactions

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10
Q

What is amplitude?

A

The maximum dispacement of a wave from rest/normal/equilibrium position

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11
Q

What is wavelength?

A

The distance between two identical points on a wave ie. the distance for one complete wave cycle

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12
Q

What is time period?

A

The time taken for one complete wave cycle

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13
Q

What is frequency?

A

The number of wave cycles per second

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14
Q

What does frequency equal?

A

1/time period or wave speed/wavelength

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15
Q

What does time period equal?

A

1/ frequency

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16
Q

What is phase?

A

A measure of how far through a cycle a wave has got e.g. 1/2 a cycle is 180 degrees and 1 cycle is 360 degrees

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17
Q

What is constructive superposition?

A

If waves meet in phase, they construct to produce increased amplitude

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18
Q

What is destructive superposition?

A

If waves meet out of phase, they destruct to produce zero amplitude

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19
Q

What does wave speed equal?

A

frequency x wavelength

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20
Q

What does wavelength equal?

A

wave speed/frequency

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21
Q

What speed do all elctromagnetic waves travel at in a vacuum?

A

3.0 x 10^8 m/s

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22
Q

At around what speed do sound waves travel?

A

3.0x10^2 m/s in air at sea level

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23
Q

What is the wavelength of the different parts of the em spectrum?

A

10^3 , 10^-3, 10^-5, 10^-7, 10^-9, 10^-11, 10^-13

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24
Q

What are the frequencies of the different parts of the EM spectrum?

A

10^5, 10^11, 10^13, 10^15, 10^17, 10^19, 10^21

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25
Q

What is the use of radio?

A

broadcasting

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26
Q

What is the use of microwaves?

A

satellite communication

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27
Q

What is the use of infrared?

A

heating and cooking

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28
Q

What is the use of visible light?

A

seeing, visual imaging

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29
Q

What is the use of ultraviolet?

A

sun beds, security marking and forensics

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30
Q

What is the use of x-rays?

A

Medical imaging

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31
Q

What is the use of gamma?

A

sterlization and imaging

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32
Q

What is radio detected by?

A

aerials

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33
Q

What are microwaves detected by?

A

aerials

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34
Q

What is infrared detected by?

A

skin

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35
Q

What is visible light detected by?

A

retina

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36
Q

What is ultraviolet detected by?

A

skin

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37
Q

what are x-rays detected by?

A

CCDs (x-ray camera)

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38
Q

What is gamma detected by?

A

CCDs (gamma camera)

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39
Q

What are the dangers of radio?

A

none

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40
Q

What are the dangers of microwaves?

A

soft tissue damage

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41
Q

What is the danger of infrared?

A

burning

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42
Q

What is the danger of visible light?

A

retina damage

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43
Q

What is the danger of ultraviolet?

A

skin cancer

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44
Q

What is the danger of x-ray?

A

deep tissue cancers

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45
Q

What is the danger of gamma?

A

deep tissue cancers

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46
Q

WHat are radio and microwaves generated by?

A

Electrons in metals

47
Q

What are Infrared, Visible and Ultraviolet generated by?

A

Electrons in atoms

48
Q

How are x-rays generated?

A

Through the rapid deceleration of electrons

49
Q

How is gamma generated?

A

Through nuclear energy changes

50
Q

Explain how EM radiation is produced by atoms:

A
  • electrons exist at discrete energy levels in atoms
  • when the electrons gain energy, they move to higher energy levels
  • but they instaneously fall back to the lower energy levels and emit photons of energy equal to the difference between levels
  • photons are particles of EM radiation
51
Q

What increases the frequency of EM radiation?

A

The bigger the energy difference when the electrons move between energy levels

52
Q

What affect does the frequency of e.m. radiation have on the energy of the photons?

A

The higher the frequency of the radiation, the greater the energy of the photons associated with the EM radiation

53
Q

What happens to the danger of the photon as it increases in energy? Why?

A

The danger of it to human tissue increases as its additional small wavelenght makes it likely to interact with matter on a cellular and atomic level.

54
Q

How are ultraviolet photons produced in relation to electrons in atoms?

A

If electrons jump to the un-excited ground state

55
Q

How are visible photons produced in relation to electrons in atoms?

A

If electrons jump to the 1st excited state

56
Q

How is infrared produced in relation to electrons in atoms?

A

If electrons jumpt to the 2nd excited state

57
Q

What produces radiowaves?

A

the oscillation of conduction electrons in circuits

58
Q

How are radiowaves recieved?

A
  • the transverse radio waves
  • interact with electrons in a metal aerial or receiving circuit
  • causing them to oscillate at the frequency of the radio wave
  • producing an alternating current
59
Q

What em radiation causes ionisation?

A

high frequency, high energy

60
Q

What is a sievert?

A

A measure of the risk of harm resulting from body’s exposure to radiation in a dosage

61
Q

What is a black body?

A
  • a perfect absorber and emitter of EM radiation
  • emits and absorbs over the range of wavelengths of the EM spectrum
  • emit and absorb most, a wavelength linked to their temperature
62
Q

What are the key features of a cool object on an intensity-wavelength graph?

A
  • peaks at a longer wavelength

- lower intensity

63
Q

What are the key features of a hot object on an intensity-wavelength graph?

A
  • peaks at shorter wavelength

- higher intensity

64
Q

What is the best emitter and absorber of infrared radtion?

A

matt black

65
Q

What is the worst emitter and absorber of infrared radiation?

A

shiny silver/white

66
Q

Describe the experiment used to investigate the effect of colour on heating/infrared radiation:

A
  • fill a Leslie’s cube with hot water
  • monitor the temperature at each face using a thermometer
  • ensure the thermometer is a fixed distance from the cube and not actually touching it as temperature of the same metal will otherwise be measured
67
Q

What would be the expected results for the Leslie’s cube (highest to lowest relative temperature)?

A

matt black, shiny black, matt white, shiny silver

68
Q

What is the control variable in the Leslie’s cube experiment?

A

the material used for each face

69
Q

How could the equipment be improved for the leslie’s cube experiment?

A

using a IR sensitive camera/detector instead of a thermometer

70
Q

What are the laws of reflection?

A
  • Angle of incidence = angle of reflection

- object to mirror distance = mirror to image distance

71
Q

What are the properties of a reflected image?

A
  • it is the right way up
  • but laterally inverted
  • it is virtual
72
Q

What does virtual mean?

A

It cannot be projected onto a screen (ie. real)

73
Q

How do parabolic reflects reflect incident rays?

A

All to a single focus point

74
Q

WHat are parabolic reflectors used in?

A

Satellite dishes and telescopes

75
Q

Define light refraction:

A
  • a change in the speed of waves
  • when they cross the boundary
  • between mediums of different optical density
  • this results in a change in the direction of the propagation of the waves
76
Q

What happens to the velocity and wavelength of a wave as it goes crosses the boundary of an object with greater optical density?

A
  • the velocity and wavelength both reduce
77
Q

How are wave fronts and incident rays related?

A

They are perpendicular to one another

78
Q

What happens to the frequency of a wave during refraction?

A

stays the same

79
Q

What is the refractive index?

A

The ration of the speed of light in air to the speed of light in an optically more dence medium . It is equal to sini/sinr

80
Q

What is a convex (converging lens)?

A

A lens which is thicker in the middle than at the edges

81
Q

What is focal length?

A

The distance between the lens and where the principle focus is

82
Q

On what line does the principle focus focuss on?

A

The principle axis

83
Q

What happens to light hitting a convex lens?

A

It is refracted to a single principle focus point

84
Q

What must be true of an object for its image to be the same size?

A

it must be located two focal lengths away from the lens

85
Q

What happens to the image if the object is placed in between 1 and 2 focal lengths from the lens? Why is it not a magnifying glass?

A

It is magnified and inverted and real

86
Q

What has to occur for a lens to be a magnifying glass?

A

The object has to be located less than 1 focal length from the lens so that the rays diverge and their cross over is where the new larger image is formed.

87
Q

What are the properties of the image with a magnifying glass?

A
  • not inverted
  • magnified
  • virtual
88
Q

What is a concave lens?

A

A lens which is thinner in the middle than at the edges. It causes light rays to diverge

89
Q

What are the properties of an image of an object that has light passing trough a concave lens?

A
  • not inverted
  • diminished (not magnified)
  • virtual
90
Q

What are the two types of reflection?

A
  • specular

- diffuse

91
Q

What is specular reflection?

A

Reflection from mirrors which form an observable image

92
Q

What is diffuse reflection?

A

When parallel waves are scattered into different directions by a rough surface. This does not form a reflected image.

93
Q

Why can’t we see a clear image when light is reflected on a wall for example?

A
  • the wall has bumps on its surface
  • so the approaching light rays are reflected at many different angles in different directions by the wall
  • this causes a blur of light
  • this is diffuse reflection
94
Q

Why do some objects appear white?

A

Because they reflect every wavelength of light equally

95
Q

What objects reflect each wavelength equally?

A
  • white objects

- a mirror

96
Q

What is observed colour the result of?

A

Diffuse reflection and selective absorption

97
Q

What will happen to white light hitting a red filter?

A
  • the red part of the white light will be transmitted

- the orange, yellow, green, blue and violet will be absorbed

98
Q

What will happen to white light hitting red surface?

A
  • the red part of the white light will be reflected

- the orange, yellow, green, blue and violet will be absorbed

99
Q

What does each colour in the visible spectrum consist of?

A

A wide range of wavelengths. A colour is not the result of the reflection of a single wavelength

100
Q

What is the range of wavelengths for visible light?

A

400nm to 700nm continuously

101
Q

What is the difference between a water wave and a sound wave?

A

water waves are transverse and sound waves are longitudinal

102
Q

Describe how to calculate wavelength, frequency and wavespeed with a ripple tank:

A
  • count the number of waves passing a fixed point in a fixed amount of time. Time using a stopclock.
  • divide the number of waves by the time (s) to calculate the frequency of the wave
  • Measure the wavelength from a frozen image which is enabled by a photograph from a camera or stroboscope
  • do this by measuring the distance between e.g. 10 waves and divide this by the number of waves measured e.g. 10
  • repeat measurements and calculate a mean
  • calculate wave speed using: wave speed = frequency x wavelength
103
Q

What does the frequency of a string vibration depend on?

A
  • the length of the string that’s free to vibrate
  • the tension in the string (ie. the force to hold the string straight)
  • the thickness of the string
104
Q

Describe the wave speed through a solid required practical:

A
  • connect string to a vibration generator connected to a signal generator , adjusting length using a wooden bridge and maintaining tension with masses on a hanger linked to the pivot
  • adjust the frequency or wavelength of string until it looks like the waves are not moving and clear standing waves can be seen
  • measure the length of one wavelength
  • record the frequency on the signal generator
  • calculate the speed using wave speed = frequency x wavelength
105
Q

What is the relationship between wavelength and frequency of a string and why?

A

As wavelength increases, f decreases in proportion as wave speed in a string is constant for constant tension and thickness

106
Q

What are the two types if seismic waves?

A

p-waves and s-waves

107
Q

What are the properties of a p-wave?

A
  • longitudinal
  • propagate through solids and liquids
  • wave speed increases with density in earth
  • propagate through the earth rather than just on the surface
108
Q

What are the properties of an s-wave?

A
  • transverse
  • propagate in the crust
  • responsible for the aftershock in an earthquake
109
Q

Why do p-waves arrive before s-waves?

A

as p-waves are longitudinal, they take a straight line path through the earth so it’s a shorter distance

110
Q

Describe the distribution of particles in a sound wave:

A
  • there are compressions where particles are closer together and at a higher pressure
  • there are rarefactions where particles are further apart and at a lower pressure
111
Q

What determines the amplitude of a sound wave?

A
  • the extent of the compressions and rarefactions

- a higher pressured compression and lower pressured rarefaction gives a higher amplitude

112
Q

How can the speed of sound be measured?

A
  • place the visible sound source and timer a certain distance away from eachother
  • set of the soure and start timing on the visual signal given and stop timing on hearing the sound
  • the speed of sound will be the distance/time measured
113
Q

What is the greatest source of uncertainty in the speed of sound measurement? Why?

A

timing errors as unless the distance is very large, any timing error will be a large fraction of the measured time

114
Q

How is the effect of the timing error reduced when measuring the speed of sound?

A
  • increasing distance
  • for example, use echo technique: where the source and observer are the the same and the distance = 2 x distance from observer to reflecting surface

AQA GCSE Physics (9 decks)

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