Waves, Sound, and EM
Spectrum
Waves, EM Spectrum and Sound
• Describe how energy is transferred
through sound waves and how pitch and
loudness are related to wave properties of
frequency and amplitude.
An
Introduction
to Waves
• Waves: repeated disturbances in a medium
(substance) that transfers energy through it
• Medium: the material the wave travels
through (air, water, etc)
Water
Tuning fork
2 Main Types of Waves:
• Transverse wave: The matter moves up and
down as the wave travels horizontally
• Compressional (Longitudinal) wave:
Matter and wave move horizontally
Which is which? 
TRAVIS the
(transverse wave)
Caterpillar
Transverse Waves
Draw this picture of a Transverse Wave:
• Fancy words for your wave:
– Crest: highest point
– Trough: lowest point
– Wavelength (λ): length from crest to crest (or
trough to trough)
– Frequency (f): number of wavelengths that pass a
point each second A.k.a. pitch
• (1 Hertz = 1 wavelength per second)
– Period: amount of time it takes one wavelength to
pass a point
– Amplitude: measure from equilibrium position to
top of crest or bottom of trough. A.k.a. loudness
How do you measure wavelength
and frequency?
How do you measure wavelength
and frequency?
WORK ON: Waves WS
Compressional Waves
Draw this picture of a Compressional Wave:
(More terms? Yaaaaaay!!!)
Compression and Rarefaction
Compression
Rarefaction
• Wavelength (λ): From compression to
compression (or expansion to expansion)
• Frequency (f): number of wavelengths that
pass a point each second
• Period: amount of time it takes one wavelength
to pass a point
• Amplitude: more compressed it is, the more
amplitude (loudness) it has
Amplitude in
Transverse vs Compression Waves
Where is the crest? Trough?
What pattern do you notice between
wavelength and frequency?
As wavelength increases, frequency ______
As frequency increases, wavelength ______
What is wavelength?
What is frequency?
https://www.youtube.com/watch?v=Xu6hbS2TL
Sw
Relationship btw Frequency and Wavelength
(watch the volume)
https://www.youtube.com/watch?v=HVmt1DQ
WalQ
Think of your own comparison:
• A transverse wave is like ___________
• A compression wave is like ___________
• Using a slinky, how can you show a
transverse wave and a compressional
wave?
Pitch and Loudness
• Sound Intensity:
– more energy = more intensity
– more distance from source = less intensity
• Discuss: Which of the above waves has high
intensity?
• Loudness (decibel or dB): how the ear
and brain understands sound intensity.
How the brain interprets sound waves
• http://www.educationscotland.gov.uk/resou
rces/s/sound/amplitude.asp
• Pitch: how the ear and brain understand
frequency (or wavelength)
– (high pitch of a mosquito vs low pitch of a tuba)
– Humans can hear sounds from 20 Hz to 20,000 Hz.
– (Dogs: up to 35,000Hz……Bats: up to 100,000 Hz)
– What is the relationship between pitch and
frequency?
Pipe Cleaner Wave Models
Create a Wave…
Table 1 & 3: Transverse, High freq, low amp
Table 4 &6: Compressional, high freq, high amp
Table 5 &7: Transverse, low freq, low amp
Table 2 & 8: Compressional, low freq, high amp
Line up by…
1)
2)
3)
4)
Frequency
Amplitude
Loudness
Pitch
4 corners: soft sound, loud sound, high
pitch, low pitch
Waves Lab #1
Slinkies/Snakies
• Slinky and Snaky (helical spring) used to
ask many questions about waves (4
minutes):
http://www.youtube.com/watch?v=zyqCgtvM
wfw
Sound
• Sound waves = Compressional Waves (a.k.a.
Longitudinal Waves) in the medium of air
Compression
Compression
Compression
Compression
JUST THINK:
What would sound waves “look” like? (3 min)
http://www.youtube.com/watch?v=_vYYqRVi8vY
What happens in soft sounds?
What happens in loud sounds?
Does air itself travel when a sound wave passes
through it?
Higher frequency means _______ pitch sound.
Discuss:
• Which of the above are waves?
• Which of the above are sound waves?
• Which of the above waves are heard as
LOUDER in your ear?
• Which of the above waves has a higher pitch?
Doppler Effect and Red Shift
• Doppler Effect: a change in pitch that is due to
a moving source
– Moving towards you increases frequency (pitch)
– Moving away from you decreases frequency (pitch)
HOW DOES THE SOUND CHANGE
AS IT PASSES YOU?
• What does a high
• When is the
motorcycle pitch pitch wavelength
look like?
high?
• What does a low
• When is the
motorcycle pitch pitch wavelength
look like?
low?
• How can a tuning
fork show that
sound compresses
air?
• How can a tuning
fork be used to
show the Doppler
Effect?
Car moving to the right
Tuning Fork  Evidence:
• How does the
action of a tuning
fork that is struck
and placed in
water show
evidence that
sound pushes air
and travels in
waves?
• How does a tuning
fork that is rapidly
moved (closerfurther-closerfurther) from your
ear show the
Doppler Effect?
Redshift
• the Doppler Effect on light emitted from
moving planets!
• When planets move away from you, the
wavelength gets longer and more RED!!
• When planets move towards you, the
wavelength gets shorter and more BLUE!!
Questions for the Doppler Video
1) How many sounds does a tuning fork
make?
2) Why did the sound change as he moved
it?
3) How many sounds does the “football”
make?
4) Why did the sound change as he moved
it?
Questions about Redshift Video
1) Why does the plane’s sound change as it
moves through the air?
2) Why are objects coming towards the
Earth blueshifted?
3) Why are objects moving away from the
Earth redshifted?
4) How does redshift give evidence for the
big bang?
• *Video with Doppler Effect Demos (3 min)*:
http://www.youtube.com/watch?v=JX_A99Bq9AI
• *Explains Doppler and Red shift (3 min)*
http://www.youtube.com/watch?v=FhfnqboacV0
• Explains Red Shift and Big Bang (3 min)
http://www.youtube.com/watch?v=y5tKC3nEx2I&lis
t=PLJ215MiUVBbOYu7uX91e8sUO40oKgDHO8
&feature=c4-overview-vl
WAVE WAR!
Each person will have a partner. Your pair will
pair up with another pair. 
You will:
• Create questions
• Exchange with another pair
• Answer
• Discuss right answers with question creators
Battle 1:
Wave Parts
1. Each pair draw 2 waves on graph paper.
2. Write 3 questions about your waves including at least
3 of the following vocabulary words:
• Amplitude
• Frequency
• Pitch
• Loudness
• Wavelength
• Crest/Trough/Equilibrium Point
• Compressional Wave
• Transverse Wave
Battle 2: Sound
Each pair creates 5 questions on sound including at
least 3 of the following vocabulary words:
• Transverse wave
• Compressional Wave
• Compression/Rarefaction
• Amplitude
• Loudness
• Frequency
• Pitch
• Medium for Sound
• Doppler Effect
Electricity and Magnetism
• Describe the properties and uses of forms
of electromagnetic radiation from radio
frequencies through gamma radiation. For
example: Compare the energy of
microwaves and X-rays.
The Electromagnetic
Spectrum:
Electromagnetic waves
• Electr = ?
• Magnetic = ?
• Electromagnetic waves:
– Like other waves: They transfer energy
– Unlike other waves: Do not need medium to
move through, can move through space! (a
vacuum)!
Properties and Uses of EM Waves
• Radio: radio, microphone to speaker, radar,
(size range: length of football field to human)
• Microwaves: microwave
(size: bumblebee to pin head)
• Infrared: thermal (a.k.a. heat!) energy
(size: Cell to bacteria)
(“EM Waves are everywhere!” cont.)
•Visible Light: the only part of the spectrum we can see
•Ultraviolet: in sunlight (helps make vitamin D! Also
makes skin cancer and cataracts)
•X-rays: X-rays of broken bones, radiation therapy (size
of an atom)
•Gamma Rays: radiation therapy (size of a nucleus)
Please record the following:
• SPEED DATING Review game
• Waves, Sound, EM Spectrum Quiz
• Introductional Video about EM waves by
NASA (5:20 min):
http://www.youtube.com/watch?v=cfXzwh3K
adE
Do When Quiz is Complete
1. Turn in any missing work. (Most haven’t
turned in the following assignment.)
a. On a piece of graph paper Draw three
transverse waves of your choice. For Each wave:
b. Label (Crest, wavelength, amplitude, trough)
c. Write a sentence describing whether your
wave would have a high/low
pitch, and
high/low amplitude.
e. Extra Credit -- Include measurements of your
wave in cm (1 square = 0.5 cm
2. Work on other homework quietly.