Waves
7th grade science
Introduction
• Audience:
• Objective:
This lesson is for students in 7th grade.
Students will be able to identify a wave,
understand that a wave is produced by vibrations in
matter and demonstrate how waves transfer energy
when they interact with matter.
Sound
• Where does sound come from?
• Where do you hear sound in the
world around you?
Click the ?
Sound
• Where does sound come from?
• Where do you hear sound in the
world around you?
Click the ?
Sound
• Where does sound come from?
• Where do you hear sound in the
world around you?
Click the ?
Sound
• Where does sound come from?
• Where do you hear sound in the
world around you?
How does sound travel?
• We have an idea of where sound
comes from, but how does it get
from where it is to us so we can
here it?
• How does sound travel?
?
Waves!
• Sound travels in waves. But what is a wave?
• A wave is caused when vibrations, or movement, is caused in
matter, or the stuff around us. For example, the speakers on a
radio use energy to vibrate the air around it. These vibrations
travel through the air in a wave and eventually reach your ear
which is what allows you to hear.
Let’s Explore
Sound Waves
• Sound waves are caused when
objects create vibrations. This
energy vibrates the air around it
creating a wave.
• When you pluck a guitar string,
the string vibrates and produces
a wave.
• If you look at a speaker when it
is playing you will see it vibrate.
This produces a sound wave the
same way the guitar does
True or False, a guitar string and
a speaker make a sound wave the
same way?
True
False
CORRECT!
• Both the guitar and speaker create sound waves
by making vibrations in the air
Not quite right…
• Both the guitar and the speaker make sound
waves by making vibrations in the air
Sound Waves You Can See
• Take a look at this video of a speaker creating sound waves in
water. The water allows us to see the waves that are being
created since we can’t see the air around us. (click on the link
to play video)
http://www.youtube.com/watc
h?v=_diS1twUbcU
Look for the
vibrations in the
water when the
speaker is on and
watch them stop
when the speaker
stops playing
Parts of a Wave
• Now that we know that sound travels in waves there
must be different parts of a wave because we hear
different sounds.
• There are 3 things that make up a wave.
They are
wavelength, frequency and amplitude.
Wavelength
Crest
Crest
Trough
Trough
• The wavelength is how far apart the waves are.
This can be
measure from either crest to crest or trough to trough. This is
equal to one wave length.
• Crest – top of the wave
Trough – bottom of the wave
Which letter represents the
wavelength of this wave?
A
B
A – green line
C
B – blue line
C – red line
CORRECT!
• The wavelength is the distance between two crests or
two troughs
Not quite, try again…
Remember a wavelength is either from crest to crest or trough to trough
A
B
A – green line
C
B – blue line
C – red line
Frequency
Frequency is the number of waves that travel past a point every
second. Therefore shorter wavelengths means higher
frequency and longer wavelengths means a lower frequency.
The more waves the
higher the
frequency.
(Click the speaker to listen)
Fewer waves
means a lower
frequency.
(Click the speaker to listen)
Which wave has a lower
frequency?
Red wave
Blue wave
CORRECT!
The red line is a lower frequency because it has
larger wavelengths and therefore less waves per
second.
Not quite…
Remember the frequency is the number of waves per second.
The lower the frequency, the fewer waves per second. These
waves will be more spaced out.
Go back to
review the
information
Amplitude
• The third part of waves is called the Amplitude.
The amplitude
is how much energy a wave has. If it is a sound wave then a bigger
amplitude will mean it’s a louder sound
High amplitude
Low amplitude
Which wave has a biggest
amplitude?
1
2
3
Not quite…
Remember, amplitude is based on how tall the waves are. The
taller the waves the bigger the amplitude and more energy the
wave has
High amplitude
Low amplitude
Go back to
review the
information
CORRECT!
The taller the wave the bigger the amplitude. The
bigger the amplitude the more energy a wave has.
High amplitude
Low amplitude
Different types of waves
• There are other waves besides sound waves.
Waves also move
through the water and waves known as seismic waves cause
the Earth to shake during and earthquake.
-
Waves have energy
Waves move through
matter, they do not push
matter along. For
example, waves in the
ocean are not carrying a
lot of water with them but
are simply moving
through the water. Watch
this video to learn more
about waves in the ocean
and see an example
http://www.youtube.com
/watch?v=6pVmAho2ew8
&feature=youtu.be
Waves Interacting with
Matter
When waves interact with matter, the energy they
are carrying is transferred to that object causing it
to vibrate. With sound waves that allows us to
hear and with seismic waves during earthquakes,
that can make buildings fall down. Click to the
next slide to see an example of how waves interact
with buildings and can knock them down.
Examples
Click the link below to see an
example of how waves in
earthquakes transfer energy
http://www.youtube.com/watch?v=MRNxhIa
tSec&feature=youtu.be
Quiz Time
• In the upcoming quiz you will be answer questions about the
different parts of waves, different types of waves, how waves are
made and how they interact with matter. If you aren’t sure about
any of those, go back to that section and review the material
Back to
parts of waves
Back to
Types of waves
Back to
Interacting with
matter
Back to
How waves
are made
Proceed to
the quiz
How does sound travel?
Sound moves through the air
into our ears
Sound particles enter our
ears
By loud noises
By making vibrations in the
air
Click
button to
try again
Beginning
of quiz
Try
Again
Back to
studying
Beginning
of quiz
Back to
studying
Next
Question
True or false: A speaker can create
sound with out creating vibrations?
True
False
Click
button to
try again
Beginning
of quiz
Try
Again
Back to
studying
Beginning
of quiz
Back to
studying
Next
Question
Which of these is not a part
of a wave?
The wavelength
The frequency
The threshold
The amplitude
Click
button to
try again
Beginning
of quiz
Try
Again
Back to
studying
Beginning
of quiz
Back to
studying
Next
Question
Frequency is…
The size of the wavelength
Number of waves per second
The amount of energy a wave has
None of the above
Review what we learned earlier.
Click
button to
try again
Beginning
of quiz
Try
Again
Back to
studying
Beginning
of quiz
Back to
studying
Next
Question
Waves transfer ______ to
matter it interacts with.
Water
Information
Energy
Earthquakes
Click
button to
try again
Beginning
of quiz
Try
Again
Back to
studying
Beginning
of quiz
Back to
studying
Next
Question
In this video, vibrations are
being transferred from what to
what?
Click link to
play video
Water  Speaker
Speaker  Water
http://www.youtube.com/
watch?v=_diS1twUbcU
Ground  Water
Seismic waves  Sound waves
Click
button to
try again
Beginning
of quiz
Try
Again
Back to
studying
Beginning
of quiz
Back to
studying
Next
Question
Which wave has a larger
amplitude, green or red?
Red
Green
Click
button to
try again
Beginning
of quiz
Try
Again
Back to
studying
Beginning
of quiz
Back to
studying
Next
Question
When a wave interacts with matter,
what happens?
The energy the wave is carrying is transferred
The wave moves through the matter
The wave stops moving
The matter absorbs the waves energy
Click
button to
try again
Beginning
of quiz
Try
Again
Back to
studying
Beginning
of quiz
Back to
studying
Next
Question
True or false: This is an example of a
wave.
True
False
Click
button to
try again
Beginning
of quiz
Try
Again
Back to
studying
Beginning
of quiz
Back to
studying
Next
Question
You completed the quiz.
Here’s a cool song about
Click below to go back to
waves:
the beginning to review
http://www.youtube.com/watc
the material or to retake
h?v=77slIdkkQWg
the quiz
Beginning
of material
Beginning
of quiz