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Waves Flashcards

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1
Q

What is a progressive wave?

A

A wave that transfers energy through space

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2
Q

What is a transverse wave?

A

A wave in which the oscillations are perpendicular to the direction of wave propagation

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3
Q

What is a longitudinal wave?

A

A wave in which the oscillations are parallel to. the direction of wave propagation

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4
Q

Give an example of a longitudinal wave

A

Sound, primary seismic waves

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5
Q

Give an example of a transverse wave

A

waves on a stretched string, secondary seismic waves, electromagnetic radiation

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6
Q

What are the regions of high pressure in a longitudinal wave called?

A

Compressions

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7
Q

What are the regions of low pressure in a longitudinal wave called?

A

rarefactions

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8
Q

What is the displacement of a wave?

A

The distance of a particle in the medium from its equilibrium position in a particular direction

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9
Q

What is the equilibrium position in wave motion?

A

The position of the medium when undisturbed by a wave

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10
Q

What is the amplitude of a wave?

A

Maximum displacement of the medium from the equilibrium position

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11
Q

What is the frequency of a wave?

A

The number of wave cycles per second OR the number of waves passing a point per unit time

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12
Q

What is the time period of a wave?

A

Time taken for one complete oscillation OR time for a whole wavelength to pass a fixed point

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13
Q

What is the relationship between frequency and time period?

A

f=1/T or inverse proportionality

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14
Q

How many radians of phase are there in one complete wave cycle?

A

2π rad

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15
Q

What term describes a phase difference of zero between two points on a wave?

A

In phase

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16
Q

What term describes a phase difference of pi radians between two points on a wave?

A

In anti phase

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17
Q

What is the phase difference between points half a wavelength apart?

A

180 degrees or π radians

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18
Q

What is the phase difference between points a quarter of a wavelength apart?

A

90 degrees or π /2 rad

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19
Q

What is an oscillation?

A

A displacement one way and then the other about an equilibrium position

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20
Q

What is diffraction?

A

The spreading out of waves after passing through a slit/around an obstacle

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21
Q

What effect does reducing the size of a single slit have on diffraction?

A

diffracted waves spread out more

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22
Q

What is the effect of decreasing the wavelength on diffraction?

A

diffracted waves spread out less

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23
Q

What is meant by the intensity of a wave?

A

Intensity is the energy delivered by the wave per second per square metre normal to the wave

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24
Q

How is the intensity of a wave related to the amplitude?

A

Intensity is proportional to amplitude squared

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25
Q

How does intensity vary with distance from a point source of waves

A

inverse square law or I=P/4 π r^2

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26
Q

What is a mechanical wave

A

A wave that requires a medium

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27
Q

What is the difference between mechanical waves and electromagnetic waves?

A

EM waves don’t require a medium

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28
Q

What is an electromagnetic wave?

A

An oscillation of the electric and magnetic fields at right angles to each other

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29
Q

What is the speed of all EM waves in a vacuum/air?

A

3x10^8 ms^-1

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30
Q

List the regions of the EM spectrum in order of increasing wavelength

A

Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, Gamma rays

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31
Q

Which two regions of the EM spectrum overlap?

A

X-rays and gamma rays

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32
Q

State the range of wavelengths (in powers of ten) of radio waves

A

> 10^-1

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33
Q

State the range of wavelengths (in powers of ten) of microwaves

A

10^-1 - 10^-3

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34
Q

State the range of wavelengths (in powers of ten) of infrared

A

10^-3 - 10^-6

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35
Q

state the range of wavelengths of visible light

A

7x10^-7 - 4x10^-7

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36
Q

State the range of wavelengths (in powers of ten) of ultraviolet

A

10^-7 - 10^-8

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37
Q

State the range of wavelengths (in powers of ten) of X-rays

A

10^-8 - 10^-13

38
Q

State the range of wavelengths (in powers of ten) of gamma rays

A

<10^-10

39
Q

Why can’t longitudinal waves be polarised?

A

longitudinal waves already only have a single direction of oscillation

40
Q

What is the effect of a polarising filter?

A

It only transmits the component of the oscillations parallel to the filter

41
Q

What is the effect of perpendicular polarising filters?

A

No light is transmitted

42
Q

Give a use of polarising filters

A

LCD screens, 3D TV, polarimetry in manufacturing, anti-glare sunglasses

43
Q

What effect does reflection have on the polarisation of light?

A

Reflected light is partially polarised in the plane of the surface

44
Q

What effect does scattering light have on polarisation?

A

Scattered light is polarised

45
Q

Which wave property always remains constant when a wave travels from one medium to another?

A

Frequency

46
Q

When entering a material with a higher refractive index what happens to wave speed?

A

decreases

47
Q

When entering a material with a lower refractive index what happens to wavelength?

A

increases

48
Q

What is the definition of the refractive index of a material?

A

a value calculated from the ratio of the speed of light in a vacuum to that in a second medium of greater density

49
Q

What are the angles of incidence and refraction measured relative to?

A

The normal to the boundary

50
Q

Which way do waves refract when entering a material with a higher refractive index?

A

Toward the normal

51
Q

Which way do waves refract when entering a material with a lower refractive index?

A

Away from the normal

52
Q

What is the angle of refraction at the critical angle?

A

ninety degrees

53
Q

What are the conditions required for total internal reflection?

A

Wave must be travelling in a material with a higher index and meeting a boundary with a material of lower refractive index.The angle of incidence must be greater than the critical angle

54
Q

What two phenomena occur when a wave goes from a higher to a lower refractive index at an angle of incidence less than the critical angle?

A

The ray is refracted and partially reflected

55
Q

What is the principle of superposition?

A

When two waves meet at a point the resultant displacement is the (vector) sum of the displacements of the individual waves

56
Q

What is constructive interference?

A

When two waves superpose in phase causing an increase amplitude

57
Q

What is destructive interference?

A

When two waves superpose in anti phase causing a decreased amplitude

58
Q

What are coherent sources of waves?

A

sources that emit waves with a constant phase difference (and the same frequency)

59
Q

What is an interference pattern?

A

A pattern of regions of constructive and destructive interference produced by coherent sources of waves

60
Q

What path difference is required for waves to be in phase?

A

a whole number of wavelengths

61
Q

What path difference is required for waves to be in anti phase?

A

An odd number of half wavelengths

62
Q

What is the relationship between path difference and phase difference for coherent sources?

A

(Path difference/wavelength)x2π

63
Q

What term describes a phase difference of zero between two waves?

A

In phase

64
Q

What term describes a phase difference of π radians between two waves?

A

In anti phase

65
Q

What is x in the double slit equation ( λ=ax/D)

A

Fringe seperation

66
Q

What is D in the double slit equation (λ=ax/D)

A

Distance between the double slits and the screen

67
Q

What is a n the double slit equation (λ=ax/D)

A

Distance between the double slits

68
Q

What occurs to cause a dark fringe in the double slit experiment?

A

Destructive interference of the light from each slit

69
Q

What occurs to cause a bright fringe in the double slit experiment?

A

constructive interference of the light from each slit

70
Q

What did Youngs double slit experiment demonstrate about the nature of light?

A

that light exhibits wave behaviour

71
Q

What name is given to light of a single frequency/wavelength?

A

Monochromatic

72
Q

Why did Young place a single slit before the double slit?

A

To ensure the light from each of the double slits was in phase

73
Q

What are the conditions required for a stationary wave to form?

A

Two waves travelling/propagating in opposite directions superposé with same frequency and similar amplitude

74
Q

What is an antinode on a stationary wave?

A

A point where the progressive waves are in phase and constructively interfering resulting in maximum amplitude

75
Q

What is a node on a stationary wave?

A

A point where the progressive waves are in anti phase and are destructively interfering resulting in minimum amplitude

76
Q

How many wavelengths are there between adjacent nodes of a standing wave?

A

Half a wavelength

77
Q

What is the phase difference between points either side of a node?

A

Pi rad/180 degrees

78
Q

What is the phase difference of points between two adjacent nodes?

A

Zero

79
Q

How does phase vary along a progressive wave

A

Changes continuously across each wave cycle

80
Q

How does amplitude vary in a stationary wave?

A

It varies continuously along the wave. It is a maximum at anti odes and a minimum at nodes

81
Q

How does amplitude vary in a progressive wave?

A

It is the same at every point along the wave

82
Q

What type of wave doesn’t transfer energy?

A

Stationary waves

83
Q

What is the fundamental frequency of a string?

A

The lowest frequency which produces a stationary wave on the string

84
Q

What factors determine the fundamental frequency on a string?

A

Length, tension and the thickness of the string

85
Q

Progressive wave

A

transfer of energy as the result of oscillations of the medium through which the energy is travelling

86
Q

longitudinal wave

A

the oscillation of particles is parallel to the direction of travel of the wave

87
Q

transverse wave

A

the oscillation of particles is perpendicular to the direction of travel of the wave

88
Q

mechanical waves

A

energy is transferred through a medium

89
Q

displacement

A

the distance moved from equilibrium for a point on a wave

90
Q

amplitude

A

the maximum displacement from the equilibrium position

91
Q

refraction

A

when a wave changes direction as it enters a new medium, due to a change in the speed of travel

92
Q

critical angle

A

angle of incidence that will produce an angle of refraction of 90 degrees

Physics (13 decks)

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