Physics Chapter 5, Section 4
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Transcript Physics Chapter 5, Section 4
Physics Chapter 5, Section 4
Sounds from Vibrating Air
HW: p 526 #1, 4-6
Learning Objective
Explain how sound is produced by
longitudinal compression waves
Write a conclusion that includes IV,
DV, evidence, and the big idea
Success Criteria
Identify standing waves in different
kinds of air-filled tubes
Observe how pitch changes with the
length of the tube
Observe the effect of closing one end
of the tube on the pitch of the sound
Observe sound bending around
corners and spreading
Relate observations of pitch to
drawings of standing waves
Organize observations to find a pattern
Do Now
Write LO and SC on
new left page
p 518 WDYS/WDYT
Agenda
Do Now
Investigation 5.4
Summary
Investigation 5.4
Part A (groups)
1-3 - with straws
4, 5 with test tubes
Part B
1 - Class demo
2 - with group
Part C
In groups
HW: p 526 #1, 4-6
Learning Objective
Explain how sound is produced by
longitudinal compression waves
Write a conclusion that includes IV, DV,
evidence, and the big idea
Success Criteria
Identify standing waves in different kinds of
air-filled tubes
Observe how pitch changes with the length
of the tube
Observe the effect of closing one end of the
tube on the pitch of the sound
Observe sound bending around corners and
spreading
Relate observations of pitch to drawings of
standing waves
Organize observations to find a pattern
Do Now
How did closing the
end of the tube
change the sound?
Agenda
Do Now
Investigation 5.4
Summary
Physics Talk 5.4
What kind of waves
does sound make?
Compressional
(longitudinal) waves
How does this relate
to springs?
QuickTime™ and a
decompressor
are needed to see this picture.
Physics Talk 5.4
What was the
medium the sound
traveled through?
The air in the straw
or tube
Physics Talk 5.4
How do these related
to the standing
waves created by the
stringed instrument?
Air molecules cannot
vibrate at the bottom of
the test tube, so this is a
node of the wave
The open end of the test
tube provides the wave’s
amplitude
The vibration of the air at
this end, is the sound you
hear
This is the antinode of the
wave
Physics Talk 5.4
What is diffraction?
The ability of sound
waves to spread out
or change direction
as the emerge from
an opening
This is why you can
hear someone talking
around a corner
Physics Talk 5.4
The top show a large
amount of diffraction,
when the opening is
smaller
The bottom shows a
small amount of
diffraction, since the
opening is larger
Physics Talk 5.4
How do megaphones
work?
A megaphone
increases the
diffraction of sound,
due to the small
opening you tell into
The best opening size
depends on the
sound being
produced
Vibrating Columns of Air
QuickTime™ and a
decompressor
are needed to see this picture.
Physics Talk
How does changing
wavelength effect
frequency?
When keeping a
constant wave speed,
increasing the
wavelength will
decrease the
frequency - causing a
lower pitch
Physics Talk 5.4
Open tube
wavelength
Closed tube
wavelength
Half of the
wavelength will fit
The wavelength is 2x
the length of the
tube
One quarter of the
wavelength will fit
The wavelength is 4x
the length of the
tube
Physics Talk 5.4
Why does the closed
straw have a lower
pitch?
Why does the open
straw have a higher
pitch?
The wavelength is
longer (4x), meaning
the frequency is
lower
The wavelength is
shorter (2x),
meaning the
frequency is higher
What do you think now?
How do flutes and organ pipes produce
sound?
USE PHYSICS!