Waves
An officer on a ship measured a wave by noticing that it was as high as a
specific point on his ship. That point was 100 feet tall!
Height is a property of all waves. All waves have a
height that we can measure.
Speed is another property of all waves. All
waves move at a speed that we can measure.
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Speed
Wavelength
And frequency
But we’ll talk more about that in a minute!
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Just like mountains have peaks, and houses
have roofs,
The top of a transverse wave is called
something special, too. It’s called a CREST.
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The CREST of a wave is the highest part of a
wave.
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CREST
Every transverse wave has a crest.
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Write down your definition of the word
“crest,” and draw a picture of a crest.
YOU WILL HAVE1 MINUTE
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The TROUGH of a transverse wave is the
lowest part of a wave.
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Every transverse wave has a trough.
TROUGH
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Write down your definition for the word
“trough,” and draw a picture.
YOU HAVE 1 MINUTE
You are on a boat.
The water is starting
to get kind of rough.
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When your boat is pointing upwards, you are
climbing to the crest of the wave.
When your boat is pointing downward and
sinking lower, you are falling to the trough of
the wave.
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The AMPLITUDE is the distance between the
middle of the wave (or the resting position)
and the crest.
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Amplitude
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The AMPLITUDE can also be measured by the
distance between the middle of the wave and
the trough.
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Amplitude
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The amplitude of a wave is important,
because it lets us know how much energy a
wave is carrying.
Bigger amplitude = More energy
Smaller amplitude = Less energy
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What is the amplitude of this wave?
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How did you find the amplitude?
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Which wave has the highest amplitude?
What is the amplitude of wave A?
A
2
1
B
0
0
-1
-2
5
10
15
Compressional
Longitudinal
wave
On a compressional wave
the area squeezed
together is called the
compression. The areas
spread out are called the
rarefaction.
The wavelength is the
distance from the center of
one compression to the
center of the next
compression.
Frequency is the number of waves
(vibrations) that pass through a point in
one second.
Period is the time it takes for one full
wavelength to pass a certain point.
Frequency is waves per second.
1
frequency 
period
1
f
T
Frequency is the number of bumps in a given
space or time.
YOU HAVE 2 MINUTES TO ANSWER THE QUESTIONS
IN YOUR NOTEBOOK
1. What is the frequency of the wave in the picture on the left?
2. What is the frequency of the wave in the picture on the right?
What is wavelength?
Wavelength is a measure of distance, so the
units for wavelength are always distance units,
such as meter, centimeters, millimeters, etc.
A wave moving through a medium travels at a certain
speed.
Wave speed is usually measured in meters/second
Wave speed = frequency x wavelength.
Try it out!!
1. A wave is 8 meters long and has a frequency of 3
Hz. Find speed.
2. In the ocean, a wave has a wavelength of 4 m and
a frequency of 2 Hz. What is the wave’s speed?