STUDY GUIDE: This is an overview of what is to be expected for the CH 25-26 test. In addition, don’t forget to review all HW,
notes, Do Nows, etc.
Chapter 25: Vibrations and Waves
You should be able to…
You should know that…
Describe the characteristics and
properties of waves (25.2)
Wavelength is the distance between successive identical parts of a wave. Also
should know: amplitude, crest, trough. Frequency is how often a vibration occurs,
measured in hertz. Frequency is inversely proportional to period, and vice versa.
Waves transmit ENERGY, not matter
Describe wave motion (25.3)
Describe factors that affect the speed
of a wave (25.4)
Distinguish between transverse
waves and longitudinal waves (25.5,
25.6)
Distinguish between constructive
and destructive interference (25.7)
Describe how a standing wave occurs
(25.8)
Describe the Doppler effect for sound
and relate it to the blue and red shifts
for light (25.9)
Describe bow waves (25.10)
Describe sonic booms (25.11)
Wavespeed depends on the medium through which the wave travels. Wavespeed
= wavelength x frequency
Transverse: medium moves at right angles to the direction in which the wave
travels. (EM waves)
Longitudinal: medium moves back and forth parallel to the direction in which the
wave travels (sound waves)
Interference patterns occur when waves from different sources arrive eat the
same point at the same time
Constructive: crests overlap crests or troughs overlap troughs
Destructive: a crest overlaps a trough
Points of complete destructive interference (NODES - at which the medium does
not move) remain at the same location
Observed shift in frequency received due to motion of a vibrating source toward
or away from a receiver
When an object moves through a medium faster than the speed of waves in the
medium, a bow wave spreads out behind it.
Just as a bow wave is produced by overlapping circles that form a V, a shock wave
is produced by overlapping spheres that form a cone (you hear the sonic boom)
You should be able to
answer:
What is the difference between
crest and trough, wavelength
and amplitude?
Does the material move with
the wave?
Why do we see lightening and
THEN hear thunder after?
How can slinkies represent
waves?
Why is it important to design
an auditorium with “good
acoustics”?
Why does a police siren sound
different when approaching
us/driving away?
Why does thunder produce
such a loud crack?
Chapter 26: Sound
You should be able to…
26.1- Relate the pitch of a sound to its
frequency
You should know that…
The source of all sounds is a vibration. Pitch is our subjective
impression of the frequency of sound.
You should be able to answer:
Why can you still hear your cell
when it’s on vibrate?
Why is it important to not turn ipod
volume too high?
Why can’t adults hear the “mosquito
ringtone?”
How does a sound wave travel
through air?
Are movie scenes in space with the
big explosions correct?
Why do people in old western
movies put their ears to the
ground?
26.2-Describe the movement of sound through
air
26.3-Compare the transmission of sound thru
air with that thru solids, liquids, and a vacuum
26.4-Decribe factors that affect the speed of
sound
As a source of sound vibrates, a series of compressions and
rarefactions travels outward from the source
Sound needs a medium through which to travel.
Travels fastest in solids, then liquids, then slowest in gasses
The speed of sound is DIFFERENT in different media – speed in a
gas depends on the temperature and mass of particles.
26.5-Describe loudness and sound intensity
The intensity of a sound is: Objective and measured by
instruments/devices; DIRECTLY proportional to the amplitude squared of
the sound wave
Loudness is: A physiological sensation sensed in the brain, which differs for
different people; Subjective, but related to sound intensity
Why are some sounds painfully loud?
26.6-Give examples of forced vibration
Guitar’s body allows for forced vibration and louder sound
26.7-Describe natural frequency
All elastic objects have their own special set of frequencies.
26.8-Describe resonance
When an object’s forced vibration matches natural frequency
26.9-Describe how sound waves interfere with
one another
26.10-Describe beats
Constructive: add (louder)
Destructive: Subtract (softer or cancel out)
Fluctuation in loudness heard
Why are sounding boards
important?
Why do some pennies sound
different when dropped?
Why did the Tacoma Narrows
collapse?
Why do speakers sound different
depending on where you are?
Why do you hear a fluctuation
when you hum next to a fan?
Chapter 25-26 Study Guide… On your test, you will get the following formulas:
f= 1
T
T =__1__
f