This document covers various characteristics of waves including: 1) All waves transmit energy, diffract, reflect, refract, and exhibit constructive and destructive interference. 2) Diffraction is the spreading out of waves as they pass through an opening, like sound waves spreading through a doorway. 3) Refraction occurs when waves change speed as they pass into a new medium, like water waves bending as they enter shallow water. 4) Pitch is a sound wave's frequency, determining if it is high or low. Pure tones have one frequency while complex tones have multiple frequencies. 5) When waves of slightly different frequencies overlap, beats occur and disappear when the sources are in tune.

1. Lesson #5Lesson #5
Wave Characteristics
Nelson Reference Pages:Nelson Reference Pages:
393, 427, 454,393, 427, 454, 458 - 459
((Not all parts are covered by the Nelson TBNot all parts are covered by the Nelson TB))

2. General Wave Properties
 All waves exhibit the following:All waves exhibit the following:
 Transmit energy – indicated by amplitudeTransmit energy – indicated by amplitude
 Diffraction – the spreading out of wavesDiffraction – the spreading out of waves
 Reflection – echo (for sound), and (for light) mirrorReflection – echo (for sound), and (for light) mirror
reflectionreflection
 Refraction – the slowing, or speeding up, of a wave as itRefraction – the slowing, or speeding up, of a wave as it
passes into another medium. Recall this property frompasses into another medium. Recall this property from
the light unit in grade 10 science.the light unit in grade 10 science.
 Constructive and destructive interference – superpositionConstructive and destructive interference – superposition
of waves.of waves.
 Waves pass through each other. We often experienceWaves pass through each other. We often experience
this when two people are talking and we listen to onlythis when two people are talking and we listen to only
one person.one person.

3. Diffraction
 The first part of the following video shows howThe first part of the following video shows how
straight waves behave as they move through astraight waves behave as they move through a
single slit.single slit.
 http://www.youtube.com/watch?v=lIn-BLJNXpYhttp://www.youtube.com/watch?v=lIn-BLJNXpY
 The spreading out into semicircular waves isThe spreading out into semicircular waves is
called diffraction. We notice diffraction whencalled diffraction. We notice diffraction when
someone is talking in another room. The soundsomeone is talking in another room. The sound
waves spread out as they pass through awaves spread out as they pass through a
doorway and diffraction enables us to hear thedoorway and diffraction enables us to hear the
person in the other room.person in the other room.

4. Refraction of Water Waves
 The following videos show water wavesThe following videos show water waves
changing direction as they slow down whenchanging direction as they slow down when
passing into shallow water. Recall that whenpassing into shallow water. Recall that when
water waves move into shallow water this is likewater waves move into shallow water this is like
moving into another medium.moving into another medium.
 http://www.youtube.com/watch?v=7BIc7Oonru0http://www.youtube.com/watch?v=7BIc7Oonru0
 http://www.youtube.com/watch?v=Bf1k9-4bb4whttp://www.youtube.com/watch?v=Bf1k9-4bb4w

5. Pitch and Sound Quality
 Pitch refers to how high or low a sound is. Thisrefers to how high or low a sound is. This
refers to the frequency of the sound.refers to the frequency of the sound.
 Pure sound results when only one naturalresults when only one natural
frequency is present. Tuning forks, andfrequency is present. Tuning forks, and
synthesizers can generate this type of sound.synthesizers can generate this type of sound.
(The wave form is often represented as a pure(The wave form is often represented as a pure
sine wave.)sine wave.)
 Sound quality results when 2 or more naturalresults when 2 or more natural
frequencies combine to form a complex wavefrequencies combine to form a complex wave
form.form.

6. In the graph above, two natural frequencies wereIn the graph above, two natural frequencies were
used to create the complex wave form (yellowused to create the complex wave form (yellow
graph). To do this, the “y” values from the firstgraph). To do this, the “y” values from the first
and second overtones were added together toand second overtones were added together to
generate the “y” values for the complex wave.generate the “y” values for the complex wave.
Creation of Complex Wave
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Fundamental
1st Overtone
Complex Wave

7. Interference of Waves with slightly
different f , (( & slightly different λ))
 {Students may choose to download a free frequency{Students may choose to download a free frequency
generator at:generator at: http://www.nch.com.au/tonegen/index.html?http://www.nch.com.au/tonegen/index.html?
gclid=CMDVqrfS8qoCFUUBQAodIHY5OAgclid=CMDVqrfS8qoCFUUBQAodIHY5OA }}
 The website below will be used for demonstrationThe website below will be used for demonstration
purposes (& theory explanation).purposes (& theory explanation).
 http://www.school-for-champions.com/science/sound_beat_frequencies.htmhttp://www.school-for-champions.com/science/sound_beat_frequencies.htm
 Hearing Test:Hearing Test:
 http://www.youtube.com/watch?v=hvkipAlRKq0http://www.youtube.com/watch?v=hvkipAlRKq0
 Musicians often use beats to tune their instruments.Musicians often use beats to tune their instruments.
When the beats disappear the instrument is in tune. ToWhen the beats disappear the instrument is in tune. To
calculate the beat frequency, the following:calculate the beat frequency, the following:
fb = |f1 - f2|,
HereHere fb is the beat frequency and equals the absoluteis the beat frequency and equals the absolute
value ofvalue of f1 - f2

8. Sound as a Compression Wave
 See video for tuning fork:See video for tuning fork:
http://www.youtube.com/watch?v=bomzzHC-59khttp://www.youtube.com/watch?v=bomzzHC-59k
 The video describes the two parts of theThe video describes the two parts of the
compression (longitudinal) wave as being:compression (longitudinal) wave as being:
compression and rarefaction. These parts cancompression and rarefaction. These parts can
be represented as a sinusoidal wave form.be represented as a sinusoidal wave form.
 (You may also refer to the web page:(You may also refer to the web page:
http://www.mediacollege.com/audio/01/sound-waves.htmlhttp://www.mediacollege.com/audio/01/sound-waves.html
 and http://www.fi.edu/fellows/fellow2/apr99/soundvib.htmland http://www.fi.edu/fellows/fellow2/apr99/soundvib.html

9. Speed of Sound in Air
 The speed of sound in air can be found from theThe speed of sound in air can be found from the
following equation:following equation: v = 331 + 0.59TC ,,
(The Nelson TB uses a slightly different
equation: v = 331.4 +0.606TC. You may use
either equation)
HereHere v is measured in m/s andis measured in m/s and TC is the airis the air
temperature in degrees Celsius.temperature in degrees Celsius.
By referring to theBy referring to the Table 1 onon page 395, it can be, it can be
seen thatseen that sound travels fastest in solids, slower
in liquids, and slowest in gases. We can alsoWe can also
see that sound travels about 4.3 times faster insee that sound travels about 4.3 times faster in
fresh water at 20fresh water at 2000
C than in air at the sameC than in air at the same
temperature.temperature.

10. Practice Questions
Nelson Textbook Questions:
Page 393 # 1-3Page 393 # 1-3
Page 429 # 1-3Page 429 # 1-3
Page 442 # 8, 9Page 442 # 8, 9
Page 460 # 1
Questions from McGraw-Hill TB:
1.1. Sound can be described in terms of loudness,Sound can be described in terms of loudness,
pitch, and quality. a.) Explain how eachpitch, and quality. a.) Explain how each
concept enables you to differential sounds. b.)concept enables you to differential sounds. b.)
How is each of these characteristicsHow is each of these characteristics
represented in the sound wave?represented in the sound wave?

11. McGraw-Hill questions continued.
2. On a crisp fall day, a cottager looks across the
lake and sees a neighour chopping wood. He
notices that there is a time delay of 2.1 s between
the time the axe hits the log and when he hears
the sound of its impact. If the air temperature is
8.0 0
C, how far is he from the his neighbour?
{Ans 7.1 x 10 2
m}
3. A guitar player is his guitar to A 440.0 Hz
on the piano. He hears 14 beats in 4.0 s
when he plays A on his guitar. a.) What two
frequencies might he be playing? b.) How
could the guitarist determine which
frequency he was playing? {Ans. 443.5 Hz
and 436.5 Hz, Discuss}