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Physics > Sound And Waves > Flashcards

Sound And Waves Flashcards

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1
Q

Do mechanical waves need a medium

A

Yes

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2
Q

What is the name for how mechanical waves are made?

A

Made by a disturbance in the medium

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3
Q

What is a disturbance

A

A source of energy causing a vibration

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4
Q

How do mechanical waves cause a disturbance in the medium?

A

They pass along a medium causing the particles of the medium to vibrate, this is passed from one particle to its Neighbour

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5
Q

What is the overall motion of particles in mechanical waves

A

Zero

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6
Q

3 examples of mechanical waves

A

Sound waves
Ultrasound waves
Waves on water

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7
Q

Do electromagnetic waves need a medium?

A

No

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8
Q

Can electromagnetic waves pass through a medium?

A

Yes, but travel faster in a vacuum

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9
Q

What do electromagnetic waves consist of ?

A

Varying electric and magnetic fields

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10
Q

3 examples of electromagnetic waves

A

Light
Radio waves
X-rays

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11
Q

What do progressive waves consist of

A

Energy moving away from a source

Energy is transferred from one place to another

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12
Q

1 example of progressive wave

A

From our voices

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13
Q

Is there a difference between progressive waves and standing waves

A

Yes

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14
Q

In a transverse wave the medium and energy are…

A

At right angles to each other

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15
Q

Transverse wave

A

The direction in which the energy travels is perpendicular to the direction of vibration or the particles of the medium

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16
Q

Lambda

A

Wavelength

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17
Q

Wavelength of a transverse wave

A

The distance between 2 successive crests

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18
Q

f

A

Frequency

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19
Q

Unit of wavelength

A

Meter

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20
Q

Frequency

A

The Number of complete oscillations (top of one crest to the next ) made by a point in one second

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21
Q

Unit of frequency

A

Hertz (Hz)

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22
Q

Amplitude

A

The maximum displacement of a particle of the medium from its mean position

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23
Q

c

A

Speed of wave

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24
Q

Speed of wave =

A

Frequency x wavelength

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25
Q

c=

A

f x lambda

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26
Q

Longitudinal wave

A

The direction in which the energy travels is parallel to the direction of vibration of the particles of a medium

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27
Q

Regions of high particle density of a longitudinal wave

A

Compressions

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28
Q

Regions of low particle density of a longitudinal wave

A

Rarefactions

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29
Q

Wavelength of a longitudinal wave

A

Distance between 2 successive compressions

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30
Q

Speed of radio wave

A

Equal to speed of light, not sound

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31
Q

Speed of light

A

3 x 10 8 m/s

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32
Q

Speed of sound

A

340 m/s

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33
Q

Source

A

Origin of wave

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34
Q

Ray

A

A line which shows the direction of travel of the wave

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35
Q

Wavefront

A

Concentric circles around the source

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36
Q

Wavelength on a wavefront

A

Distance between 2 consecutive wavefronts

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37
Q

Diffraction

A

The spreading if a wavefront into the geometrical shadow when it passes through a gap or around an obstacle

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38
Q

Diffraction is much more noticeable when

A

The size of the gal or obstacle is approximately equal to or less than the wavelength of the wave

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39
Q

Why do sound waves easily diffract as they pass through an open door

A

Because the wavelength of a sound wave is approximately equal to the width of an open door

40
Q

How can you demonstrate the diffraction is light waves

A

Using a diffraction grating

41
Q

What is the limit on how thin a fiber can be seen through an optical microscope

A

No smaller than the wavelength of light

42
Q

Interference

A

When waves from coherent sources meet and combine

43
Q

Constructive interference

A

Gives a wave of greater amplitude

44
Q

Destructive interference

A

Gives a wave of smaller amplitude

45
Q

Coherent sources

A

Emit waves of the same frequency and the waves are in phase or have a constant phase difference

46
Q

In phase

A

Syncronised

47
Q

Condition for constructive interference

A

Waves are in phase and have the same frequency

The crest of one wave meets the crest of another

48
Q

Condition for destructive interference

A

When the waves meet they are out of phase with a path difference of lambda over 2 or a multiple of this
The crest of one wave meets the trough of another

49
Q

Use of destructive interference

A

Noise reduction

50
Q

Stationary waves arise from

A

The combining of 2 progressive waves of the same amplitude, frequency and speed and moving in opposite directions

51
Q

Energy and standing waves

A

Large amounts of energy are stored in standing waves, there is no transmission of energy

52
Q

2 places stationary waves are produces

A

On the strings of string instruments

In the air columns of wind instruments

53
Q

Node

A

Part of standing wave that doesn’t move

54
Q

Antipode

A

Part of a standing wave that moves like crazy

55
Q

The wavelength of a stationary wave

A

Twice the distance between successive nodes

(Or twice the distance between 2 successive antinodes

56
Q

How do we knew that sound is a wave?

A

Interference is a phenomenon associated with waves. Sound exhibits interference, therefore it is a wave

57
Q

A box that makes noise

A

Signal generator (SG)

58
Q

Displays frequencies on a screen

A

Oscilloscope

59
Q

Why is CO2 used to show the refraction of sound

A

It’s the perfect density for the experiment

60
Q

Doppler effect

A

The apparent change in the frequency of a wave due to the relative motion between the source and the observer

61
Q

source moving towards observer 3

A

Wavefronts closer together
Smaller observed wavelength
Observed frequency is higher

62
Q

Source moving away from observer 3

A

Wavefronts further apart
Observed wavelength longer
Observed frequency lower

63
Q

fo =

A

fsc
—
c +/- u

64
Q

Is rise and fall of frequency due to Doppler effect symmetrical

A

No

65
Q

How to change angular speed to linear speed

A

v = rw

66
Q

Moving towards observer

A

-

67
Q

Moving away from observer

A

+

68
Q

Star moving towards earth

A

Looks blue

69
Q

Star moving way from earth

A

Looks red

70
Q

2 medical uses of Doppler effect (only used when asked for)

A

Echocardiogram - blood flow measurement

Ultrasound - foetal heartbeat

71
Q

2 uses of Doppler effect

A

Checking the speed of a car

Studying the stars

72
Q

2nd harmonic =

A

1st overtone

73
Q

5th harmonic =

A

4th overtone

74
Q

Pitch

A

Related to the frequency of a sound

Higher frequency = higher pitch

75
Q

Quality of a sound

A

Depend of the number and intensity of harmonics present

76
Q

Loudness of a sound

A

Depends on the amplitude of the vibrations of a sound wave

Subjective

77
Q

3 characteristics of a sound

A

Pitch
Quality
Loudness

78
Q

When a system that is capable of vibrating is made it vibrate

A

It will do so at its natural frequency

79
Q

Forced frequency

A

External vibration force acts on a system that is capable of vibrating at that frequency

80
Q

What is resonance

A

The transfer of energy between 2 bodies of the same natural frequency

81
Q

When does resonance happen

A

When the forced frequency is equal to the natural frequency

82
Q

T=

A

2pi root (l over g)

83
Q

f =

A

1/T

84
Q

f

A

Frequency

85
Q

l

A

Length of string

86
Q

T

A

Tension

87
Q

u

A

Mass per unit length

88
Q

n

A

Number of harmonic

89
Q

How do you see resonance on a string

A

Paper rider falls off

90
Q

Open close pipe under the fraction line

A

4

91
Q

Open open pipe under the fraction line

A

2

92
Q

Good quality instrument and why

A

Open open pipe

Can have all harmonics

93
Q

d

A

End correction

94
Q

How do you get d

A

I internal diameter x .3

95
Q

What do you measure diameter with

A

Sliding callipers

96
Q

how do you get u from the graph of frequency of a stretched string against 1/length

A 
slope = f/1/l = f x l
u = t/4l squared f squared 
u = T/4(slope) squared
97
Q

how do you get u from the graph of frequency of a stretched string against root T

A 
slope = f/root T
u = (1/4lsquared)(T/f sqaured)= (1/4lsquared)(rootT/f) squared
u = (1/4l sqaured) x (1/slope)squared

Physics (11 decks)

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