Sound And Waves

Question 1

Do mechanical waves need a medium

Answer 1

Yes

Question 2

What is the name for how mechanical waves are made?

Answer 2

Made by a disturbance in the medium

Question 3

What is a disturbance

Answer 3

A source of energy causing a vibration

Question 4

How do mechanical waves cause a disturbance in the medium?

Answer 4

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

Question 5

What is the overall motion of particles in mechanical waves

Answer 5

Zero

Question 6

3 examples of mechanical waves

Answer 6

Sound waves
Ultrasound waves
Waves on water

Question 7

Do electromagnetic waves need a medium?

Answer 7

No

Question 8

Can electromagnetic waves pass through a medium?

Answer 8

Yes, but travel faster in a vacuum

Question 9

What do electromagnetic waves consist of ?

Answer 9

Varying electric and magnetic fields

Question 10

3 examples of electromagnetic waves

Answer 10

Light
Radio waves
X-rays

Question 11

What do progressive waves consist of

Answer 11

Energy moving away from a source

Energy is transferred from one place to another

Question 12

1 example of progressive wave

Answer 12

From our voices

Question 13

Is there a difference between progressive waves and standing waves

Answer 13

Yes

Question 14

In a transverse wave the medium and energy are…

Answer 14

At right angles to each other

Question 15

Transverse wave

Answer 15

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

Question 16

Lambda

Answer 16

Wavelength

Question 17

Wavelength of a transverse wave

Answer 17

The distance between 2 successive crests

Question 18

f

Answer 18

Frequency

Question 19

Unit of wavelength

Answer 19

Meter

Question 20

Frequency

Answer 20

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

Question 21

Unit of frequency

Answer 21

Hertz (Hz)

Question 22

Amplitude

Answer 22

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

Question 23

c

Answer 23

Speed of wave

Question 24

Speed of wave =

Answer 24

Frequency x wavelength

Question 25

c=

Answer 25

f x lambda

Question 26

Longitudinal wave

Answer 26

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

Question 27

Regions of high particle density of a longitudinal wave

Answer 27

Compressions

Question 28

Regions of low particle density of a longitudinal wave

Answer 28

Rarefactions

Question 29

Wavelength of a longitudinal wave

Answer 29

Distance between 2 successive compressions

Question 30

Speed of radio wave

Answer 30

Equal to speed of light, not sound

Question 31

Speed of light

Answer 31

3 x 10 8 m/s

Question 32

Speed of sound

Answer 32

340 m/s

Question 33

Source

Answer 33

Origin of wave

Question 34

Ray

Answer 34

A line which shows the direction of travel of the wave

Question 35

Wavefront

Answer 35

Concentric circles around the source

Question 36

Wavelength on a wavefront

Answer 36

Distance between 2 consecutive wavefronts

Question 37

Diffraction

Answer 37

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

Question 38

Diffraction is much more noticeable when

Answer 38

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

Question 39

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

Answer 39

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

Question 40

How can you demonstrate the diffraction is light waves

Answer 40

Using a diffraction grating

Question 41

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

Answer 41

No smaller than the wavelength of light

Question 42

Interference

Answer 42

When waves from coherent sources meet and combine

Question 43

Constructive interference

Answer 43

Gives a wave of greater amplitude

Question 44

Destructive interference

Answer 44

Gives a wave of smaller amplitude

Question 45

Coherent sources

Answer 45

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

Question 46

In phase

Answer 46

Syncronised

Question 47

Condition for constructive interference

Answer 47

Waves are in phase and have the same frequency | The crest of one wave meets the crest of another

Question 48

Condition for destructive interference

Answer 48

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

Question 49

Use of destructive interference

Answer 49

Noise reduction

Question 50

Stationary waves arise from

Answer 50

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

Question 51

Energy and standing waves

Answer 51

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

Question 52

2 places stationary waves are produces

Answer 52

On the strings of string instruments | In the air columns of wind instruments

Question 53

Node

Answer 53

Part of standing wave that doesn’t move

Question 54

Antipode

Answer 54

Part of a standing wave that moves like crazy

Question 55

The wavelength of a stationary wave

Answer 55

Twice the distance between successive nodes | (Or twice the distance between 2 successive antinodes

Question 56

How do we knew that sound is a wave?

Answer 56

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

Question 57

A box that makes noise

Answer 57

Signal generator (SG)

Question 58

Displays frequencies on a screen

Answer 58

Oscilloscope

Question 59

Why is CO2 used to show the refraction of sound

Answer 59

It’s the perfect density for the experiment

Question 60

Doppler effect

Answer 60

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

Question 61

source moving towards observer 3

Answer 61

Wavefronts closer together Smaller observed wavelength Observed frequency is higher

Question 62

Source moving away from observer 3

Answer 62

Wavefronts further apart Observed wavelength longer Observed frequency lower

Question 63

fo =

Answer 63

fsc — c +/- u

Question 64

Is rise and fall of frequency due to Doppler effect symmetrical

Answer 64

No

Question 65

How to change angular speed to linear speed

Answer 65

v = rw

Question 66

Moving towards observer

Answer 66

-

Question 67

Moving away from observer

Answer 67

+

Question 68

Star moving towards earth

Answer 68

Looks blue

Question 69

Star moving way from earth

Answer 69

Looks red

Question 70

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

Answer 70

Echocardiogram - blood flow measurement | Ultrasound - foetal heartbeat

Question 71

2 uses of Doppler effect

Answer 71

Checking the speed of a car | Studying the stars

Question 72

2nd harmonic =

Answer 72

1st overtone

Question 73

5th harmonic =

Answer 73

4th overtone

Question 74

Pitch

Answer 74

Related to the frequency of a sound | Higher frequency = higher pitch

Question 75

Quality of a sound

Answer 75

Depend of the number and intensity of harmonics present

Question 76

Loudness of a sound

Answer 76

Depends on the amplitude of the vibrations of a sound wave | Subjective

Question 77

3 characteristics of a sound

Answer 77

Pitch Quality Loudness

Question 78

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

Answer 78

It will do so at its natural frequency

Question 79

Forced frequency

Answer 79

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

Question 80

What is resonance

Answer 80

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

Question 81

When does resonance happen

Answer 81

When the forced frequency is equal to the natural frequency

Question 82

T=

Answer 82

2pi root (l over g)

Question 83

f =

Answer 83

1/T

Question 84

f

Answer 84

Frequency

Question 85

l

Answer 85

Length of string

Question 86

T

Answer 86

Tension

Question 87

u

Answer 87

Mass per unit length

Question 88

n

Answer 88

Number of harmonic

Question 89

How do you see resonance on a string

Answer 89

Paper rider falls off

Question 90

Open close pipe under the fraction line

Answer 90

4

Question 91

Open open pipe under the fraction line

Answer 91

2

Question 92

Good quality instrument and why

Answer 92

Open open pipe | Can have all harmonics

Question 93

d

Answer 93

End correction

Question 94

How do you get d

Answer 94

I internal diameter x .3

Question 95

What do you measure diameter with

Answer 95

Sliding callipers

Question 96

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

Answer 96

``` slope = f/1/l = f x l u = t/4l squared f squared u = T/4(slope) squared ```

Question 97

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

Answer 97

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