Wave Properties
Answer Me!!!
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Can you break a wine glass using only your
voice? Why?
Wave Fronts
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Imagine a pebble dropped into a lake.
Waves don’t travel only in one direction from
the pebble.
Waves spread out in concentric circles from
the pebble.
Each solid circle represents
the crest of a wave.
All of the points on one crest
are called a wave front.
Resonance
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Objects vibrate at a specific frequency when
the object is hit, touched, etc.
If two objects have the same natural
frequency (resonance frequency), one will
begin to vibrate if the other is struck.
Opera singer breaking glass
Tacoma Narrows Bridge
Tuning forks
Practice Problem

A tuning fork oscillates with a frequency of
256 Hz after being struck by a rubber mallet.
Which phrase best describes the sound
waves produced by this oscillating tuning
fork?
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Electromagnetic waves that require no medium
Electromagnetic waves that require a medium
Mechanical waves that require no medium
Mechanical waves that require a medium
Practice Problem 4
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A nearby object may vibrate strongly when a
specific frequency is emitted from a
loudspeaker. What is this phenomena?
Diffraction
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Diffraction is the spreading of a wave into a
region behind a barrier.
A small opening in
the barrier will
produce a
pronounced
diffraction pattern
If the opening in the
barrier is larger than
the incoming
wavelength, there
will be no diffraction.
Answer Me!!!

As motorcycle drives by you, what sound
does it make? Why?
Doppler Effect
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As the source of a constant frequency wave moves
towards an observer, the wave’s observed
frequency will be higher than the wave’s actual
frequency.
As the source of a constant frequency wave moves
away from an observer, the wave’s observed
frequency will be lower than the wave’s actual
frequency.
The higher the relative velocity, the more the
observed frequency will change.
http://www.lon-capa.org/~mmp/applist/doppler/d.htm
Doppler Effect - Sound
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Frequency of sound is observed as pitch.
Higher frequency = Higher pitch
Lower frequency = Lower pitch
Doppler Effect - Light
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Frequency of light is observed as color.
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Higher Frequency = towards violet
Lower Frequency = towards red
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Practice Problem 4
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How can a radar gun effectively use the
Doppler effect to measure velocity of
oncoming vehicles?
Practice Problem 1

A 2.00 x 106 Hz radio signal is sent a
distance of 7.30 x 1010 m from Earth to a
spaceship orbiting Mars. The spaceship is
moving away from Earth when the radio
signal is received. Compared to the
frequency of the signal sent from Earth, the
frequency of the signal received will be
Practice Problem 3
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A source of sound waves approaches a
stationary observer through a uniform
medium. Compared to the frequency and
wavelength of the emitted sound, the
observer would detect waves with a
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Higher frequency and shorter wavelength
Higher frequency and longer wavelength
Lower frequency and shorter wavelength
Lower frequency and longer wavelength
Summarize
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On a separate sheet of paper, describe the
Doppler effect and how it is observed in
sound waves and light waves.
Answer Me!!!!
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If you see lightning strike and then 5 seconds
later you hear the thunderclap from that
strike, how far away from you did that
lightning strike.
Superposition
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Superposition takes place when two or
more waves travel through the same medium
at the same time.
Constructive Interference
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When two waves are both positively (or both
negatively) displaced constructive interference
takes place.
Maximum constructive interference takes place
when both waves are in phase
Destructive Interference
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When one wave is positively displaced and the
second wave is negatively displaced, destructive
interference takes place.
Maximum destructive interference takes place
when waves are 180o out of phase
Pulses in the Same Medium
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When two pulses pass through the same
medium at the same time, they will interfere
with each other.
Standing Waves
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Standing waves are made when two waves
of the same amplitude and frequency travel in
opposite directions in the same medium. In a
standing wave, antinodes and nodes are
stationary.
Practice Problem 1
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Two pulses approach each other in a uniform
medium. Draw the superposition of the two
pulses.
Answer Me!!!
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Slowly walk through the aisles of the
classroom. Then write down what you
observe.
Two Source Interference
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The figure below shows the interference pattern
coming from two point wave sources.
Constructive interference takes place when the
same kind of lines meet.
Destructive interference takes place when dashed
line meets solid line
Interference Pattern
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You can also determine whether destructive
or constructive interference is taking place at
a point by counting the number of
wavelengths from each of the sources
Practice Problem 2
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The diagram below represents water waves
of length l from two point sources. What is
the difference in length between the paths
from each source to point P?
P
Practice Problem 3
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Two monochromatic, coherent light beams of
the same wavelength converge on a screen.
The point at which the beams converge
appears dark. Which phenomena best
explains this effect?