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A level Physics > Unit 2.4 - The Nature of Waves > Flashcards

Unit 2.4 - The Nature of Waves Flashcards

1
Q

Progressive waves

A

A pattern of disturbances travelling through a medium and carrying energy with it

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2
Q

What does a progressive wave involve?

A

The particles of the medium oscillating about their equilibrium position

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3
Q

Oscillating

A

Vibrating

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4
Q

Equilibrium position of a particle

A

Mid point of oscillations

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5
Q

Definition of a wave

A

Transfer energy without any transfer of matter

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6
Q

When is energy transferred with a wave?

A

As the wave propagates

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7
Q

What happens as a wave propagates?

A

Energy is transferred from 1 point in the medium to another

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8
Q

What are the types of progressive waves?

A

Transverse or longitudinal

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9
Q

What types of waves are transverse and longitudinal waves?

A

Progressive

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10
Q

Transverse waves

A

Oscillations (of the particles) are at right angles to the direction of travel of the wave

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11
Q

Example of transverse waves

A

Electromagnetic waves

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12
Q

Draw a diagram to present a transverse wave

A

(See notes)

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13
Q

Draw a diagram to represent a longitudinal wave

A

(See notes)

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14
Q

In which direction are the oscillations in transverse waves?

A

Perpendicular to the direction of propagation of the wave

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15
Q

Longitudinal waves

A

Oscillations (of the particles) are parallel to the direction of travel of the wave

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16
Q

In which direction are the oscillations in a longitudinal wave?

A

In the same direction as the propagation of the wave

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17
Q

Example of longitudinal waves

A

Sound waves

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18
Q

Draw a graph and label the wavelength, amplitude and 1 complete wave cycle of the wave on it

A

(See notes)

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19
Q

Displacement (m) (in terms of waves)

A

The instance of a particle form its equilibrium position at any instant

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20
Q

Amplitude

A

The maximum value of displacement

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21
Q

Amplitude symbol

A

A

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22
Q

Which feature of a wave is the same at all point?

A

Amplitude

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23
Q

Wavelength

A

The minimum distance between 2 points of a wave which are oscillating in phase

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24
Q

Wavelength symbol

A

(Lambda)

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25
Q

Frequency symbol

A

f

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26
Q

Frequency

A

The number of cycles of a wave that pass a given point in 1 second, which is the same as the number of oscillations performed per second by any particle in the medium through which it is travelling

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27
Q

Unit of frequency

A

Hertz (Hz)

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28
Q

What is 1Hz equivalent to?

A

1 wave per second/1 cycle per second

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29
Q

Period symbol

A

T

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30
Q

Period

A

The time taken for one complete cycle

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31
Q

Period equation

A

T = 1/f

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32
Q

What’s f in T = 1/f?

A

Frequency

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33
Q

What’s T in T = 1/f?

A

Period

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34
Q

Speed of a wave

A

The distance that the wave profile moves per unit time

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35
Q

Waves in phase

A

2 waves that have the same frequency and are at the same point in their cycles at the same time

36
Q

When are wave sources in phase?

A

If as they leave the sources, the waves have the same frequency and are at the same point in their cycles at the same time

37
Q

Antiphase

A

2 points are said to be in antiphase if they are at opposite points in their cycle at the same time

38
Q

If a wave is neither in phase or antiphase, what is it in?

A

“Out-of-phase”

39
Q

Draw a diagram to explain what a radian is

A

(See notes)

40
Q

Radian

A

An arc equivalent to the length of the radius
The natural unit for angle measurement

41
Q

What can we talk about between ANY 2 points on a wave?

A

Phase difference

42
Q

What is a complete cycle of a wave equivalent to in terms of radians and in degrees?

A

2πrad
360 degrees

43
Q

How much are 2 points oscillating in phase in a wave separated by (radians and degrees)?

A

2πrad
360 degrees

44
Q

How much are two points oscillating in antiphase out of phase in radians and degrees?

A

πrad
180 degrees

45
Q

How out of phase in radians and degrees are two points in a wave that are a quarter of a wave apart?

A

π/2
90 degrees

46
Q

How do we calculate the speed of a wave?

A

c = f(lambda)

47
Q

Where does the c = f(lambda) come from?

A

Speed = distance/time

Specific case where the distance moved by the wave is exactly equal to 1 wavelength
Therefore, the time elapsed must equal the period

Speed = distance/time ——> speed = (lambda)/period

Inputting into T = 1/f, using c as the symbol for speed…
c = f(lambda)

48
Q

What can the equation c = f(lambda) be used for?

A

Any type of wave

49
Q

How would we set up plane waves in water?

A

Ripple tank

50
Q

Wavefronts

A

A surface over which the phase of the wave is constant

51
Q

Draw a diagram of plane waves as a series of wavefronts

A

(See notes)

52
Q

3 features of wavefronts

A

Have all points oscillating in phase
The distance between successive wavefronts is equal to the wavelength of the waves
Are at right angles to the direction of travel (propagation) of the waves

53
Q

Draw and label a graph of displacement against position

A

(See notes)

54
Q

What are the two types of wave graphs we can get?

A

Displacement against position
Displacement against time

55
Q

What type of wave can be represented using a displacement position or displacement time graph?

A

Transverse

56
Q

What actually IS the displacement against position graph of a wave?

A

A snapshot (a picture of a wave at a particular time) of a transverse wave

57
Q

What can we easily determine from a displacement position graph?

A

Wavelength

58
Q

Draw and label a displacement against time graph for a wave

A

(See notes)

59
Q

What does a displacement against time graph for a wave show?

A

Displacement of any one particle (or point on the wave) against time

60
Q

What can we easily determine from a displacement against time graph?

A

Amplitude and period

61
Q

What can be calculated from a displacement time graph and how?

A

Frequency = 1/period

Speed = wavelength/period or frequency x wavelength

62
Q

On what type of graph can frequency and speed of a wave be easily calculated?

A

Displacement against time

63
Q

Polarised wave

A

A transverse wave in which particle oscillations occur in only one of the directions or planes at right angles to the direction of wave propagation

64
Q

Draw a diagram to represent a polarised wave

A

(See notes)

65
Q

Draw a diagram to represent an unpolarised wave

A

(See notes)

66
Q

What type of waves is it not possible to polarise?

A

Longitudinal

67
Q

Give examples of things than emit unpolarised light

A

The sun
Domestic light bulbs

68
Q

Unpolarised light

A

Oscillations take place in many directions or planes at once

69
Q

What does a Polaroid sheet/polarising filter do?

A

Only allows oscillations in 1 direction to pass through

70
Q

What can we use to only allow oscillations in 1 direction to pass through?

A

Polaroid sheet/polarising filter

71
Q

What happens to all other oscillations when unpolarised waves are passed through a polarising filter?

A

Absorbed

72
Q

Draw a diagram to represent what polarising filters do

A

(See notes)

73
Q

What happens when a second polarising sheet is rotated when light is passing through it?

A

The intensity of light through it varies

74
Q

How do we ensure maximum brightness with Polaroid sheets?

A

Line them up parallel

75
Q

What happens to the brightness through a Polaroid sheet when 2 are lined up parallel?

A

Maximum brightness

76
Q

What happens to the brightness through a second Polaroid sheet if they’re lined up perpendicular to each other?

A

Zero brightness (darkness)

77
Q

How would we get zero brightness (darkness) through a second Polaroid filter?

A

Line it up perpendicular to the other one

78
Q

definition of a progressive wave

A

a pattern of disturbances travelling through a medium and carrying energy with it
involves the particles of the medium oscillating in their equililbrium positions

79
Q

definition of a progressive wave

A

a pattern of disturbances travelling through a medium and carrying energy with it
involves the particles of the medium oscillating in their equililbrium positions

80
Q

Do waves with longer or shorter wavelengths bend the most?

A

Longer

81
Q

What’s it important to make reference to when discussing progressive waves?

A

That it travels from one point in the medium to another

82
Q

What happens in terms of phase with an increased distance from the source with progressive waves?

A

Phase lag steadily increases with distance from the source

83
Q

Describe the energy in an unpolarised wave

A

All directions have the same energy
The energy in any component is 50% of the total

84
Q

How do we work out the wavelength if we’re given the distance between, for example, 4 wavefronts?

A

Distance
—————
3

(Not 4 - draw it out and see that there’s 3 wavelengths)

85
Q

What happens to the frequency and wavelength of waves as they travel from deep to shallow water and the propagation speed is less? Why?

A

Frequency status the same - the same number of waves pass any point (they haven’t been spontaneously created or destroyed)
Smaller wavelength (c = f x wavelength)

A level Physics (29 decks)

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