1 of 40 © Boardworks Ltd 2008
© Boardworks Ltd 20082 of 40
3 of 40 © Boardworks Ltd 2008
What causes sound?
The tuning fork vibrates and you hear a sound.
Sounds are made when an object vibrates.
Take a tuning fork and strike it against a block of wood.
What do you observe?
Sound travels because the vibrating object makes nearby particles vibrate.
Sound needs a medium to travel through – it cannot pass through a vacuum.
4 of 40 © Boardworks Ltd 2008
• BELL TASK: Draw a star diagram (mind map) with the word WAVE at the centre and suggest 4 other EXAMPLES of WAVE with the names and pictures.
Module 2.2 Topic 1: 21/04/23
WavesWavesObjectives: Describe waves Describe waves and and Understand the movement of wavesUnderstand the movement of waves..
WAVE
e.g. Wave for surfing
e.g. Mexican Wave
5 of 40 © Boardworks Ltd 2008
Describing Wave
• Write down the keywords that we can use to describe waves:
•Crisp•Vibrate•Back-and-forth•Powerful•Up-and-down•Saying-goodbye•Transfer Energy•Block Energy•Push-and-Pull•Crests-and-Troughs
6 of 40 © Boardworks Ltd 2008
Simulation of a transverse wave
7 of 40 © Boardworks Ltd 2008
•A Slinky can be used to model transverse waves, by moving one end of the Slinky up and down.
What do transverse waves look like?
•The wave travels away from the source. The direction of the wave is at right angles to the movement of the source.
•source moves•up and down
•direction of wave
•coils vibrate•up and down
•In a transverse wave, the coils do not travel horizontally, each coil of the Slinky just vibrates up and down.
8 of 40 © Boardworks Ltd 2008
•trough
•peak
•The high points of a transverse wave are called peaks and the low points of a transverse wave are called troughs.
•wavelength
•wavelength
•wavelength
•amplitude
•amplitude •The amplitude of any wave is the highest or the lowest points from the rest point.
•The wavelength of any wave is the distance between two matching points on neighbouring waves.
9 of 40 © Boardworks Ltd 2008
Crests
Troughs
Amplitude
Wavelength
Twice the Amplitude
10 of 40 © Boardworks Ltd 2008
Label the picture with the keywords
Crest
Trough
Amplitude
Wavelength
11 of 40 © Boardworks Ltd 2008
4th Task of the lesson – Watch the simulations and answer the questions:
1.What happened when a pulse of wave is sent to a fixed end?It gets reflected back on the opposite side.2.What happened when a pulse of wave is sent to a loose end?It gets reflected back on the same side.3.GOLD Challenge! What is different when we send a many waves to a loose and then a fixed end?The waves get reflected stronger!
12 of 40 © Boardworks Ltd 2008
Summary: show Mr. Tsui your answers for VIVO’s!• Describe transvers waves.
• What happens to transvers waves when they hit an end?
13 of 40 © Boardworks Ltd 2008
•The wavelength of any wave is the distance between two matching points on neighbouring waves.
Wavelength of a transverse wave
•The wavelength is the same whichever two matching points are used to measure this distance.
•wavelength
•wavelength
•wavelength
•The symbol used to represent wavelength is .
14 of 40 © Boardworks Ltd 2008
•The amplitude of any wave is the maximum distance a point moves from its rest position.
Amplitude of a transverse wave
•The amplitude of a transverse wave is the height of a peak or trough from the wave’s rest position of the wave.
•amplitude
•amplitude
•The larger the amplitude, greater the energy of the wave.
15 of 40 © Boardworks Ltd 2008
MONDAY = KEYWORD DAYBELL TASK:Match and copy the meanings of the NEW keywords
BRONZE: Describe longitudinal waves?SILVER: Explain how sound wave changes?
How do Sound Wave Travel?Friday 21 April 2023
Watch the Video and Match the Boxes
17 of 40 © Boardworks Ltd 2008
Good vibrations!
What vibrates so that each of these objects makes sound?
harp stringslute strings
drum skin
mouth blowing horn
18 of 40 © Boardworks Ltd 2008
How does sound travel through the air?
19 of 40 © Boardworks Ltd 2008
Copy and complete
• Something vibrates
• Object’s vibration pushes air particles along
• Air particles push each other along and make a longitudinal wave
20 of 40 © Boardworks Ltd 2008
If we connect an mp3 player to a speaker, we can all hear the sound produced.
‘Seeing’ sound waves
If we also connect an oscilloscope to the mp3 player then we can ‘see’ the sound waves.
speaker oscilloscope
21 of 40 © Boardworks Ltd 2008
A sound can be quiet or loud.
Loudness and amplitude
On an oscilloscope trace, the loudness of a sound is shown by the height of the wave. This is called the amplitude. Which word should be crossed out in this sentence:
The larger the amplitude of the wave on the trace, the louder/quieter the sound.
quiet sound loud sound
22 of 40 © Boardworks Ltd 2008
A sound can be high or low – this is the pitch of the sound.
Pitch and frequency
On an oscilloscope trace, the pitch of a sound is shown by how many waves there are. This is called the frequency. Which word should be crossed out in this sentence:
low pitch high pitch
The greater the frequency of the waves on the trace, the lower/higher the pitch.
23 of 40 © Boardworks Ltd 2008
Which trace represents the loudest sound?
Which wave is the loudest and highest?
Sound A has the largest amplitude (i.e. the tallest waves), so it is the loudest of these two sounds.
Which trace represents the sound with the highest pitch?
Sound B has the greater number of waves across the oscilloscope – it has the highest frequency and so has the highest pitch.
A B
A B
24 of 40 © Boardworks Ltd 2008
Amplitude and wavelength
25 of 40 © Boardworks Ltd 2008
Describing sound waves
26 of 40 © Boardworks Ltd 2008
Sound waves summary
© Boardworks Ltd 200827 of 40
28 of 40 © Boardworks Ltd 2008
This investigation for calculating the speed of sound should be carried out in a quiet open space.
Speed of sound – experiment
1. When you see the cymbals crash, press start.
2. When you hear the cymbals crash, press stop.
100 m
One student should hold a stopwatch, whilst another should be holding some cymbals 100 metres away.
29 of 40 © Boardworks Ltd 2008
Experiment
Record the results of the sound experiment in a table like this:
Speed of sound – results
100 0.34 2941
2
3
4
Distance (m) Time (s) Speed (m/s)
How are these values used to estimate the speed of sound?
=100
0.34294 m/s=speed =
distance
time
30 of 40 © Boardworks Ltd 2008
The first cymbal experiment gives an estimate for the speed of sound as 294 m/s.
Speed of sound – analysis
Use the average of your results to calculate another estimate for the speed of sound.
1. How does this calculation for the average speed of sound compare with the real speed?
2. What errors could have affected the results of the cymbals experiment?
3. Do you think the speed of sound in water is the same as the speed of sound in air?
31 of 40 © Boardworks Ltd 2008
Energy transfer
How many different energy transfers do you think take place during this experiment?
When the sound waves reach the ear, there is a transfer of kinetic energy from the air particles to the eardrum.
kinetic energy of cymbals
kinetic energy of air particles
kinetic energy in eardrum
When the cymbals crash there is a transfer of kinetic energy from the cymbals to the air particles.
32 of 40 © Boardworks Ltd 2008
Sound needs a substance through which to travel because it travels by making particles vibrate.
Sound in different materials
Which state of matter does sound travel fastest through?
The particles in a solid are closer together than in a gas, and more tightly bound than in a liquid. This means vibrations are more easily passed from particle to particle, and so sound travels faster.
Sound waves travel fastest through solids.
33 of 40 © Boardworks Ltd 2008
Sound waves in different materials
34 of 40 © Boardworks Ltd 2008
Speed of sound in different materials
35 of 40 © Boardworks Ltd 2008
Which of these travel faster than the speed of sound in air?
Breaking the sound barrier
The jet fighter and the meteorite travel faster than the speed of sound in air.
This is called breaking the sound barrier.
120600small aeroplane
jet fighter
cheetah
meteorite
Distance (m)
5
Time (s) Speed (m/s)
900
50
10,000
2
2.5
0.35
450
20
28,571.4
© Boardworks Ltd 200836 of 40
37 of 40 © Boardworks Ltd 2008
What happens when a sound wave meets a hard flat surface?
Reflected sound
The sound wave is reflected back from the surface.
This is called an echo.
38 of 40 © Boardworks Ltd 2008
Plan an investigation to measure the speed of sound using echoes.
Investigating echoes
Remember to make sure it is a fair test.
You may use any of the following equipment:
stopwatch
hard, flat surfacestarting pistol
clapper board
39 of 40 © Boardworks Ltd 2008
Calculate the speed of sound for each of your distances using the formula below.
speed =distance
time
1. How do your calculations compare with the actual speed of sound in air?
2. Which of your distances gave the most accurate answer?
3. Were there any errors in your experiment?
4. Could you improve the experiment in any way to make it even more accurate?
Analysing your results
© Boardworks Ltd 200840 of 40
41 of 40 © Boardworks Ltd 2008
How do we hear?
42 of 40 © Boardworks Ltd 2008
How does the ear work?
6.The auditory nerve takes the signals
to the brain.
1. Sound waves are collected by the outer ear (or pinna).
3. The waves reach the eardrum and make it vibrate.
4. The small bones (ossicles) amplify the vibrations.
5. The cochlea turns these into electrical signals.
2. The waves travel along the ear canal.
43 of 40 © Boardworks Ltd 2008
The ear and hearing summary
44 of 40 © Boardworks Ltd 2008
Hearing range can be tested using a pitch sweep, in which the frequency of a sound wave is gradually increased. This can be created using a signal generator and loudspeaker.
What range of frequencies can you hear?
What is the hearing range of a healthy young person?
Humans can only hear sounds of certain frequencies. The range of frequencies a person can hear is called their hearing range.
20 Hz to 20,000 Hz
45 of 40 © Boardworks Ltd 2008
Does everyone have the same hearing range?
Hearing ranges and hearing loss
We all have slightly different hearing ranges.
Almost 1 in 5 people suffer some sort of hearing loss.
Temporary hearing loss may be caused by ear infections and colds, after which hearing recovers.
Permanent hearing loss and deafness can be present at birth or occur if the ear is damaged or diseased.
People lose the ability to hear sounds of high frequency as they get older.
46 of 40 © Boardworks Ltd 2008
Hearing ranges
A device has been developed called a ‘Mosquito’ which emits sounds of around 20,000 Hz.
This is audible, and potentially quite annoying, for teenagers who may be loitering around the shop, but is not noticeable to older customers.
As we get older, our ability to hear high pitched sounds deteriorates. Some shopkeepers use this to their advantage.
Some human rights groups have claimed that the devices demonise young people indiscriminately. Others claim they are a cheap, non-violent way to deal with troublesome yobs.
What do you think?
47 of 40 © Boardworks Ltd 2008
Should ‘Mosquitoes’ be banned?
48 of 40 © Boardworks Ltd 2008
Animals’ hearing ranges
49 of 40 © Boardworks Ltd 2008
Ordering volumes
50 of 40 © Boardworks Ltd 2008
Reducing noise
© Boardworks Ltd 200851 of 40
52 of 40 © Boardworks Ltd 2008
Glossary
53 of 40 © Boardworks Ltd 2008
Anagrams
54 of 40 © Boardworks Ltd 2008
Multiple-choice quiz