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Chapter 13 & 14: Waves & Sound
Waves (13.7)
A wave is a disturbance that carries ________________ through __________________ or
____________________.
Longitudinal Wave – Particles vibrate _________________ to the direction of the wave.
Transverse wave – Particles vibrate __________________ to the direction of the wave.
Defining Terms:
_______________________ : maximum displacement from equilibrium.
________________________:time it takes to execute a complete cycle of motion
________________________:number of cycles or vibrations per unit of time (Hz = sec-1)
________________________: material through which a disturbance travels.
________________________: a wave whose propagation requires a medium.
________________________: a wave whose propagation does not require a medium.
________________________: a single non-periodic disturbance.
________________________: a wave whose source is some form of periodic motion.
________________________: wave pattern that results when two waves of the same f, , and A travel
in opposite directions and interfere.
WAVE ANATOMY:
Transverse wave:
Longitudinal wave: (Draw and label compressions and rarefactions)
Sound wave (type of longitudinal wave):
Sound is a type of Longitudinal wave (14.1 & 14.2)
 Sound is a______________________________

Sound is a _____________________________

Sound is formed by a series of ______________________ and
____________________________
Frequencies of Sound:
Infrasonic Sound (elephants can hear)
Audible Sound (humans can hear)
Ultrasonic Sound (dolphins can detect)
Pitch

How high or low we perceive a sound to be, depending on the _______________
__________________________

As the frequency of a sound _______________, the pitch of that sound _______________.

Images produced by __________________ show more detail then those produced with
_____________________.
Amplitude
The _____________ of a sound wave corresponds with how ____________ the sound is.

A ________________ amplitude is a _________________ sound.

A ________________ amplitude is a _________________ sound.
Practice:
Draw a loud and high pitched wave.
Draw a loud and low pitched wave.
Draw a quiet sound wave with medium pitch
Calculating wave speed: (13.8)
Formula 1: In general
Sample Calculation 1
A tuning fork produces a sound with a frequency of ______________ Hz. The speed of sound in water
is ____________ m/s. Calculate the wavelength produced by this tuning fork in water.
Speed of a wave on a string (13.9)
Formula 2:
_______________ in the string (F)
_________________ () (mass of string per unit length) of the string
Speed of Sound in a medium (14.3)
Sound travels fastest in _________________ because ___________________________
_______________________________________ and slowest in ______________ because ___________
____________________________________________________________________________________
To find a table of the speed of sound in different mediums/materials, look on p. 461 in the textbook.
To calculate the speed of sound through air at different temperatures:
331 m/s is the speed of sound a 0oC
T = Temperature in Kelvin (K = oC + 273)
Wave interactions/interference: (13.10 & 14.7 & 14.11)
___________________________: any interference in which waves combine so that the resulting wave
is bigger than the original waves. (Crest meets crest or trough meets trough)
___________________________: any interference in which waves combine so that the resulting wave
is smaller than the largest of the original waves. (crest meets trough)
Interference of sound waves leads to a phenomena known as beats
 When two different frequencies of sound are added together the resulting wave has varying
amplitude. This varying amplitude is heard as beats.
The frequency of the resulting beats can be calculated by: (two different frequencies)
Example: A certain piano key is suppose to vibrate at 440 Hz. To tune it, a musician rings a 440 Hz
tuning fork at the same time as he plays the piano note and hears 4 beats per second. What frequency is
the piano emitting if the note the piano plays is too high?

Beats can also occur from two sources playing the same frequency
Interference from two sources at the same frequency:
Draw waves for constructive interference:
Draw waves for destructive interference:
n=0
n=0
n=1
n=1
For constructive interference, crests must
line up with crests. Therefore, the different
distances the two different waves travel
must be a whole number of wavelengths.
For destructive interference, crests must
line up with troughs. Therefore, the different
distances the two waves travel must be
different by half a wave (or some integer +
half a wave)
r1 & r2 = path length;
 = wavelength
r2-r1 = difference in path length
n = integer number of wavelengths
Example: The stars are point sources generating waves with the same frequency and the same amplitude.
The two sources are in phase with each other, so they generate wave crests at the same instant. The
wavelength of the waves are equal to the distance between the two sources. A person is standing at the
“X.” (A) What type of interference is the person experiencing?
(B) Where should the right-hand point source be placed so the person at the “X” experiences total
______________ interference?
Example: Two speakers with the same frequency are placed 3.00 m apart. A listener is originally at
point O, which is located 8.00 m from the center of the line connecting the two speakers. The listener
then walks to point P, which is a perpendicular distance 0.350 m from O, before reaching the first
minimum in sound intensity. What is the frequency of the speakers? (speed of sound in air is 343 m/s)
Reflection: (13.11)
__________________________: when a wave bounces back off a boundary
Free end reflection:
Picture: Incident (incoming) wave
Reflected wave:
Explanation:
Fixed end reflection:
Picture: Incident (incoming) wave
Explanation:
Reflected wave:
Standing Waves & Resonance: (14.8, 14.9 & 14.10)
___________________________: a wave form caused by interference that appears not to move along
the medium and that shows some regions of no vibration (nodes) and other of maximum vibration
(antinodes).
Picture of a standing wave:
Standing Waves & Resonance:

The wave pattern that results when two waves of the same f, l, and A travel in opposite directions
and interfere.

The ___________________ of the two waves appears to be ___________________.

Resonance is the tendency of a system to vibrate with _________________ at a certain
_________________.

When a system is in resonance, a small input of _______________ leads to a
________________________________.
Harmonics:
•
Sometimes more than one size wave will fit the given parameters. These different wave sizes are
called _________________.
•
First harmonic (or fundamental frequency) is the ______________ wave that fits the parameters.
•
_____________ harmonic (first overtone) is the second largest wave that fits the parameters.
•
Harmonics are one octave apart.
•
The first harmonic is the _____________________ and higher harmonics have ______________
Types of Parameters:
Two sides open
End Parameter:
Antinode
Antinode
One side open & one
side closed
Node
Antinode
Both sides closed
(string)
Node
Node
Example:
Fundamental
Frequency
(First harmonic)
Second Harmonic
(first overtone)
Third Harmonic
(second overtone)
Example: A flute is designed to play middle C (262 Hz) as the fundamental frequency when all the holes
are covered. Approximately how long should the distance be from the mouthpiece to the far on of the
flute? (assume speed of sound is 345 m/s and a flute is open at both ends).
Example: Resonance in a tube: Tuning fork with frequency of 958 Hz. What is the length (L) of tube out
of the water? (Assume the speed of sound is 345 m/s.)
Doppler Effect: (14.6) *only the concept is needed for the AP test, not the equation
The Doppler effect occurs because relative motion between the _______________ of waves and the
___________________ creates a change in ______________________.
Pictures of the Doppler effect:
Imagine sitting inside a car. The car’s horn has a frequency of 500 Hz.

What frequency would you hear inside the car, moving at 25 mi/hr?
•
As the car approaches you, is the frequency higher or lower then 500 Hz?
•
As the car passes and leaves you behind, is the frequency higher or lower then 500 Hz?
The picture shows various positions of a child on a swing moving toward a person on the ground who is
blowing a whistle. Rank positions A-E from highest to lowest frequency of the whistle heard by the
child. (A and E are NOT at the maximum height of the swing)
When an object is moving faster then the speed of sound it is called supersonic. The sound waves pile
up behind the object creating a sonic boom.
Picture of super sonic motion: