3 Waves, Sound and EM Spectrum

Question 1

An ambulance is producing sound represented by wave 2

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

Answer 1

Wave 3.

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

Question 2

What is the use of UV radiation?

Answer 2

produced by tanning bed lights to tan skin

used to detect conterfeit money

Question 3

Give three properties (features) common to all EM waves

Answer 3

They all…

travel at the speed of light

all transverse waves

all transfer energy and information without transferring matter

all travel through a vacuum

Question 4

Which wave has the largest wavelength?

Answer 4

wave 1

largest distance between adjacent crests

Question 5

How can you make a transverse wave with a slinky?

Answer 5

Move your hand in a side to side movement

Question 6

List the EM spectrum in order of decreasing frequency

Answer 6

Gamma

X-ray

UV

Visible

IR

Microwave

Radio

Question 7

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

Answer 7

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

Question 8

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

Answer 8

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

Question 9

How is wavespeed, wavelength and frequency related?

Answer 9

wavespeed = wavelength x frequency

Question 10

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

Answer 10

Question 11

What is 204 nm in m?

Answer 11

204 x 10^-9 m

Question 12

What is the Doppler effect?

Answer 12

The apparent** change in frequency (wavelength) of sound (or light) due to **relative movement between an object an observer.

Question 13

How can you make a longitudinal wave with a slinky?

Answer 13

move your hand in a forwards and backwards movement

Question 14

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

Answer 14

Higher than normal frequency as car approaches

Lower than normal frequency as car move away

Black horizontal line is the actual frequency of the sound

Question 15

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

Answer 15

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

frequency = 10 waves / time for 10 waves to pass

Question 16

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?

Answer 16

Wave 1.

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

Question 17

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

Answer 17

frequency = 10 waves/ 5 s

= 2 Hz

Question 18

What is 700 micrometres in metres?

Answer 18

700 x 10^-6 m

Question 19

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

Answer 19

Time period = 5 seconds / 10 waves

= 0.5 seconds for one wave to pass

Question 20

Which wave has the largest amplitude?

Answer 20

wave 2

It has the largest displacement from the equilibrium

Question 21

What is the unit for time period?

Answer 21

seconds or s

Question 22

What is the unit for amplitude?

Answer 22

metres (m) or decibels(dB)

Question 23

What has a larger wavelength?

Infrared or gamma?

Answer 23

Infrared

Question 24

Match the following terms with their definition

Answer 24

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

Question 25

Why are UV waves dangerous?

Answer 25

They can damage the retina and damage eye sight They can cause skin cancer

Question 26

What is the use of microwaves?

Answer 26

produced by microwaves to cook food produced by mobile phones to communicate Produced by satellites to send signals to satellite dishes

Question 27

What is a transverse wave?

Answer 27

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

Question 28

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

Answer 28

ROY G BIV Red light-larger wavelength and lower frequency- it has less energy Blue light- smaller wavlength and higher frequency- it has more energy

Question 29

What are the uses of infrared radiation (IR)

Answer 29

emitted by ovens to cook food emitted by radiators to heat houses emitted by tv controllers to control t.v.

Question 30

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

Answer 30

As wavelength increases, frequency decreases They are inversely proportional

Question 31

What is the use of X-rays?

Answer 31

Used to detect breaks in bones used to detect crystal structure in salts

Question 32

List the EM spectrum in order of increasing frequency

Answer 32

Radio Microwave IR Visible UV X-ray Gamma

Question 33

What is 13 kHz in Hz?

Answer 33

13 x 10³ Hz

Question 34

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

Answer 34

frequency = 10 waves/ 5 s = 2 Hz wavespeed = frequency x wavelength = 2 Hz x 4 m = 8 m/s

Question 35

What is the relationship between time period and frequency?

Answer 35

time period = 1 / frequency or frequency = 1 / time period

Question 36

List the EM spectrum in order of decreasing wavelength

Answer 36

Radio Microwave IR Visible UV X-ray Gamma

Question 37

How is gamma radiation dangerous?

Answer 37

It can cause mutations in cells- cancer

Question 38

How are X-rays dangerous?

Answer 38

They can cause mutations of cells- cancer

Question 39

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

Answer 39

UV X-ray Gamma

Question 40

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

Answer 40

Question 41

How is infrared dangerous?

Answer 41

It can cause skin burns if too hot

Question 42

What is a longitudinal wave?

Answer 42

Where the oscillation is along OR parallel to the direction of wave travel.

Question 43

Give three examples of a longitudinal wave

Answer 43

sound shock wave P wave

Question 44

What are the uses of radio waves?

Answer 44

radio signal for radio radar walkie talkie signals t.v. signals

Question 45

What are the uses of gamma radiation?

Answer 45

Used to kill cancer tumours used to sterilise medical equipment emitted by radioisotope tracers to detect cancer in the body

Question 46

How do you calculate the frequency of a water wave?

Answer 46

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

Question 47

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.

Answer 47

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.

Question 48

What does monochromatic mean?

Answer 48

Light of a single wavelength or colour.

Question 49

What is 100 MHz in Hz?

Answer 49

100 x 10⁶ Hz

Question 50

What is the unit for wavelength?

Answer 50

metre or m

Question 51

Give three examples of a transverse wave

Answer 51

water wave radio, microwave, IR, UV, X ray, Gamma Seismic S wave

Question 52

List the EM spectrum in order of increasing wavelength

Answer 52

Gamma X-ray UV Visible IR Microwave Radio

Question 53

Which wave has the highest frequency?

Answer 53

wave 3 ## Footnote *it has more waves per second*

Question 54

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

Answer 54

time period = 1 / frequency time period = 1 / 50 = 0.02 seconds

Question 55

How are all the EM radiation different?

Answer 55

They have.... different wavelengths different frequencies therefore they have different uses and dangers

Question 56

What is the unit for wavespeed?

Answer 56

metre per second or m/s

Question 57

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?

Answer 57

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

Question 58

What is the use of visible light?

Answer 58

produced by light bulbs to see things produced by bioluminescent creature to attract prey

Question 59

What is the unit for frequency?

Answer 59

Hertz or Hz

Question 60

How is sound created?

Answer 60

sound is created by vibrations

Question 61

List some properties of sound

Answer 61

1. it is a longitudinal 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

Question 62

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

Answer 62

As temperature of air increases, speed of sound decreases. Particles in warm air are more spread out and collisions between particles are more difficult

Question 63

Sound is a series of compressions and rarefactions. How does the speed of sound compared in a solid, liquid and gas? Explain

Answer 63

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 efficiently_*

Question 64

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

Answer 64

* 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

Question 65

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

Answer 65

* 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

Question 66

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

Answer 66

* 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

Question 67

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?

Answer 67

- **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.

Question 68

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?

Answer 68

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

Question 69

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.

Answer 69

dolphins

Question 70

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

Answer 70

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

Question 71

What is the human hearing range?

Answer 71

20 - 20 000 Hz

Question 72

What is ultrasound?

Answer 72

Any sound over 20 000 Hz

Question 73

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?

Answer 73

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

Question 74

The distance to a storm can be calculated using the lightning seen and the thunder heard. What assumption is made in this calculation?

Answer 74

Question 75

What is the amplitude of a sound wave measured in?

Answer 75

decibels Loudness or volume

Question 76

If **low frequency** is **low pitch** sound. What is high frequency sound?

Answer 76

High frequency = high pitch

Question 77

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

Answer 77

distance between compressions decreases

Question 78

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

Answer 78

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

Question 79

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

Answer 79

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

Question 80

What type of wave is sound?

Answer 80

Longitudinal vibrations are parallel to direction of wave travel