# 3 Waves, Sound and EM Spectrum Flashcards

1
Q

An ambulance is producing sound represented by wave 2

Which wave would represent the sound an observer would hear as the ambulance approached them?

A

Wave 3.

The frequency of the sound would increase and wavelength decrease as the ambulance approached the observer.

2
Q

What is the use of UV radiation?

A

produced by tanning bed lights to tan skin

used to detect conterfeit money

used to clean water

3
Q

Give three properties (features) common to all EM waves

A

They all…

travel at the speed of light

all transverse waves

all transfer energy and information without transferring matter

all travel through a vacuum

4
Q

Which wave has the largest wavelength?

A

wave 1

5
Q

How can you make a transverse wave with a slinky?

A

Move your hand in a side to side movement

6
Q

List the EM spectrum in order of decreasing frequency

A

Gamma

X-ray

UV

Visible

IR

Microwave

7
Q

What is blueshift in terms of movement of stars or galaxies?

A

If a star is moving towards the observer, the wavelength of the light it is producing is squashed.

The observer sees light of a smaller wavelength and higher frequency- it is a different colour as it is shifted towards the blue end of the spectrum

8
Q

What is redshift in terms of movement of stars or galaxies?

A

If a star is moving away from the observer, the wavelength of the light it is producing is stretched.

The observer sees light of a larger wavelength and lower frequency- it is a different colour as it is shifted towards the red end of the spectrum

9
Q

How is wavespeed, wavelength and frequency related?

A

wavespeed = wavelength x frequency

10
Q

Label the compressions, rarefactions and wavelength on the longitudinal wave below

A
11
Q

What is 204 nm in m?

A

204 x 10-9 m

0.000 000 204 m

12
Q

What is the Doppler effect?

A

When there is a change in frequency (wavelength) of sound (or light) an object is producing as a result of it moving away or towards an observer.

13
Q

How can you make a longitudinal wave with a slinky?

A

move your hand in a forwards and backwards movement

14
Q

Sketch a graph of how frequency varies with time as an object approaches an observer, passes them and then travels away from them.

A
15
Q

How would you measure the frequency of waves passing a jetty?

A

Time how long it take for 10 waves to pass the end of the jetty

frequency = 10 waves / time for 10 waves to pass

16
Q

An ambulance is producing sound represented by wave 2

Which wave would represent the sound an observer would hear as the ambulance travelled away from them?

A

Wave 1.

The frequency of the sound would decrease and wavelength increase as the ambulance moves away from the observer.

17
Q

Fred noticed that 10 waves passed a point in 5 seconds. What is the frequency of the wave?

A

frequency = 10 waves/ 5 s

= 2 Hz

18
Q

What is 700 micrometres in metres?

A

700 x 10-6 m

0.0007 m

19
Q

What is a wavefront?

A

A wavefront connects all points on a wave which are moving in phase

20
Q

Fred noticed that 10 waves passed a point in 5 seconds. What is the period of the wave?

A

Time period = 5 seconds / 10 waves

= 0.5 seconds for one wave to pass

21
Q

Which wave has the largest amplitude?

A

wave 2

It has the largest displacement from the equilibrium

22
Q

What is the unit for time period?

A

seconds or s

23
Q

What is the unit for amplitude?

A

metres (m) or decibels(dB)

24
Q

What has a larger wavelength?

Infrared or gamma?

A

Infrared

25
Q

Match the following terms with their definition

A

frequency- the number of waves going past in one second

wavelength- the length of one repeat of the wave pattern

wave speed- how far a wave travels in one second

26
Q

Why are UV waves dangerous?

A

They can damage the retina and damage eye sight

They can cause skin cancer

27
Q

What is the use of microwaves?

A

produced by microwaves to cook food

produced by mobile phones to communicate

Produced by satellites to send signals to satellite dishes

28
Q

What is a transverse wave?

A

Where the oscillation is 90° to the direction of wave travel

29
Q

How do the waves of red light differ from waves of violet light

A

ROY G BIV

Red light-larger wavelength and lowe frequency- it has less energy

Blue light- smaller wavlength and higher frequency- it has more energy

30
Q

What are the uses of infrared radiation (IR)

A

emitted by ovens to cook food

emitted by radiators to heat houses

emitted by tv controllers to control t.v.

31
Q

What is the relationship between wavelength and frequency of a wave?

A

As wavelength increases, frequency decreases

They are inversely proportional

32
Q

What is the use of X-rays?

A

Used to detect breaks in bones

used to detect crystal structure in salts

33
Q

List the EM spectrum in order of increasing frequency

A

Microwave

IR

Visible

UV

X-ray

Gamma

34
Q

What is 13 kHz in Hz?

A

13 x 103 Hz

13 000 Hz

35
Q

Fred noticed that 10 waves passed a point in 5 seconds. The waves are 4 metres apart. What is the speed of the wave?

A

frequency = 10 waves/ 5 s

= 2 Hz

wavespeed = frequency x wavelength

= 2 Hz x 4 m

= 8 m/s

36
Q

What is the relationship between time period and frequency?

A

time period = 1 / frequency

or

frequency = 1 / time period

37
Q

List the EM spectrum in order of decreasing wavelength

A

Microwave

IR

Visible

UV

X-ray

Gamma

38
Q

A

It can cause mutations in cells- cancer

39
Q

How are X-rays dangerous?

A

They can cause mutations of cells- cancer

40
Q

Which parts of the EM spectrum is considered to be dangerous?

A

UV

X-ray

Gamma

41
Q

Label the wavelength, amplitude, crest and trough of the transverse wave below

A
42
Q

How is infrared dangerous?

A

It can cause skin burns if too hot

43
Q

What is a longitudinal wave?

A

Where the oscillation is along the direction of wave travel.

44
Q

Give three examples of a longitudinal wave

A

sound

shock wave

P wave

45
Q

What are the uses of radio waves?

A

walkie talkie signals

t.v. signals

46
Q

What are the uses of gamma radiation?

A

Used to kill cancer tumours

used to sterilise medical equipment

emitted by radioisotope tracers to detect cancer in the body

47
Q

How do you calculate the frequency of a water wave?

A

frequency = number of waves/ time for those waves to pass a point

48
Q

If a star is moving very quickly away from an observer it is possible that the light can no longer be observed with the naked eye. Explain.

A

The light’s wavelength is shifted so far to the red end of the spectrum that its wavelength is the same as infrared light and is invisible to the naked eye.

49
Q

What does monochromatic mean?

A

Light of a single wavelength or colour.

50
Q

What is 100 MHz in Hz?

A

100 x 106 Hz

100 000 000 Hz

51
Q

What is the unit for wavelength?

A

metre or m

52
Q

Give three examples of a transverse wave

A

water wave

any EM wave

S wave

53
Q

List the EM spectrum in order of increasing wavelength

A

Gamma

X-ray

UV

Visible

IR

Microwave

54
Q

Which wave has the highest frequency?

A

wave 3

it has more waves per second

55
Q

The frequency of the ticker timer is 50 Hz. What is the time between two dots it prints?

A

time period = 1 / frequency

time period = 1 / 50

= 0.02 seconds

56
Q

How are all the EM radiation different?

A

They have….

different wavelengths

different frequencies

therefore they have different uses and dangers

57
Q

What is the unit for wavespeed?

A

metre per second or m/s

58
Q

Galaxies rotate

If one side of the galaxy is moving toward us and one side is moving away from us, what would we observe in terms of the light we receive from each side of the galaxy?

A

Side moving towards us will be blueshifted, the light will have a smaller wavelength and higher frequency- shifted towards the blue end of the spectrum

Side moving away from us will be redshifted, the light will have a large wavelength and lower frequency- shifted towards the red end of the spectrum

59
Q

What is the use of visible light?

A

produced by light bulbs to see things

produced by bioluminescent creature to attract prey

60
Q

What is the unit for frequency?

A

Hertz or Hz

61
Q

How is sound created?

A

sound is created by vibrations

62
Q

List some properties of sound

A
1. it is a lonitudinal wave
2. it is created by a vibration
3. it cannot travel through a vacuum
4. it can travel through a solid, liquid or gas
5. it can have different frequencies or pitch
6. it can be reflected and diffracted
63
Q

How does speed of sound in air relate to temperature? Explain

A

As temperature of air increases, speed of sound decreases.

Particles in warm air are more spread out and collisions between particles are more difficult

64
Q

Sound is a series of compressions and rarefactions.

How does the speed of sound compared in a solid, liquid and gas? Explain

A

Sound travel faster through a solid than a liquid and gas.

Sound is a vibration which is transferred from particle to particle via collisions.

Solid particles are closer together and have stronger forces between them- vibrations are passes between particles more quickly

65
Q

How can speed of sound through air be measured in a laboratory?

A
• connect two microphones to a microsecond timer
• place the two microphones 2.00 metres apart using two metre rules
• place padding under each microphone to prevent sound travelling through the table
• create a sharp sound behind the first microphone
• record the time it takes for the sound to travel from microphone 1 to microphone 2
• repeat five times and calculate the mean time
• calculate the speed of sound through air by

s = 2.00 m / mean time

66
Q

How can speed of sound through a lab bench be measured in a laboratory?

A
• connect two microphones to a microsecond timer
• place the two microphones face down on a lab bench 2.00 metres apart using two metre rules
• create a sharp tap to the lab bench behind the first microphone
• record the time it takes for the sound to travel from microphone 1 to microphone 2
• repeat five times and calculate the mean time
• calculate the speed of sound through air by

s = 2.00 m / mean time

67
Q

How can speed of sound through air be measured in the playground?

A
• stand exactly 50.00 metres from a large wall of a building
• strike two metal bars repeatedly until a ryhthm is set up and the metal bar is being hit together at the same time the echoes returns.
• start the stopwatch on one strike and time 20 complete strikes.
• This time is how long it take the sound to travel to and from the wall 20 times or 100.00 x 20 = 2000 m
• speed of sound is s = 2000 m / time
68
Q

Speed of sound can be measured accurately using a stopwatch.

If a starting pistol is used, the people timing must start the stopwatch when they see the smoke from the pistol and then stop it when they hear the sound.

How can you ensure that the speed of sound is measured accurately and what assumption is made?

A
• very large distances must be used as human reaction time introduces large uncertainties in time measurements

The assumption is that the light reaches the person immediately.

69
Q

The position of imperfections in a metal can be located using ultrasound.

An ultrasound pulse is sent into the metal and reflections received. If the speed of sound in the metal is 5000 m/s and the echo received 20 microseconds later.

How can the distance to the imperfection be calculated?

A

20 microseconds = 0.00002 s

divide time by 2

time to imperfection = 0.00002 s / 2 = 0.00001 s

d = s x t

distance = 5000 m/s x 0.00001 s = 0.05 m or 5 cm

70
Q

Bats locate their prey by echosounding.

They use pulses of ultrasound and listen for the echo with their large ears. If the time between the pulse and echo is small, the insect is closer to the bat.

Name another animal which uses echo sounding.

A

dolphins

71
Q

When calculating the distance in an echosounding question, what is the most common error?

A

The distance calculated from the speed of sound and time for echo must be divided by two!

72
Q

What is the human hearing range?

A

20 - 20 000 Hz

73
Q

What is ultrasound?

A

Any sound over 20 000 Hz

74
Q

Ultrasound is used to image babies in the womb.

An image is formed on the screen if reflections are received from the different surfaces (layers) of the baby.

How does the time for the reflection relate to the distance to the surface?

A

The further the surface is from the ultrasound transmitter/receiver, the longer it takes for the echo to return.

75
Q

The distance to a storm can be calculated using the lightning seen and the thunder heard.

What assumption is made in this calculation?

A
76
Q

What is the amplitude of a sound wave measured in?

A

decibels

Loudness or volume

77
Q

If low frequency is low pitch sound.

What is high frequency sound?

A

High frequency = high pitch

78
Q

As the pitch of sound increases, what happens to the distance between the compressions?

A

distance between compressions decreases

79
Q

What property of ultrasound allows it to be used for cleaning?

A

Ultrasound is a vibration, the vibrations loosen dirt in hard to reach areas.

80
Q

What property of ultrasound allows it to be used to break up kidney stones?

A

Concentrated beams of ultrasound are absorbed by the kidney stone, vibrations occur in the kidney stone and this breaks it up into small pieces.

81
Q

What type of wave is sound?

A

Longitudinal

vibrations are parallel to direction of wave travel