Number off everyone at your table. (1, 2, 3

1
Number off everyone at your table. (1, 2, 3)

• Remember do not touch anything at your table
  until I have given the go-ahead!

2
Review

• Whats the difference between a transverse and
  longitudinal wave?
• What do waves transfer?
• What are the high and low points of a transverse
  wave called?
• What are the parts of a longitudinal wave where
  the particles are spread out and close together?

The way they move
Energy
Crest and Trough
Compression and Rarefaction
3
First things first

• Which of these show ONE full wave?

One wave has one crest and one trough
4
Student s 1 and 2

• Stretch the slinky out across the table.
• Student 1 Flick one end left and right once per
  second.
• Everyone observe.
• Student 2 Flick the slinky twice per second.

What happened to the waves when you flicked the
rope more often?
5
Wavelength
Distance

• What is length a measure of?
• So what do you think a wave length is?
• The distance between two waves

WAVELENGTH
WAVELENGTH
6
Which has a shorter wavelength?
7
Measuring Wavelength

• Does this tell us the distance between the two
  waves?
• Why not?

You have to measure the distance between two
comparable points! (crest to crest, trough to
trough, etc.)
8
Student s 3 and 4
Waves with _________________ wavelength have
more energy.

• Stretch the slinky out across the table.
• Student 3 You will be creating two waves one
  with a large wavelength and one with a smaller
  one. Do not tell your group members which will be
  first and second.
• Everyone observe.
• Group members guess which wave had the larger
  wavelength.
• Student 4 Repeat and allow group members to
  guess which wave had the larger wavelength.

a shorter
Which wave did you have to put more effort into
creating?
9
Amplitude

• The distance between the crest or trough and the
  waves resting position.
• Wheres the crest? Trough?

Crest
Amplitude
Resting Position
Amplitude
Trough
10
Which has a larger amplitude?
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What does amplitude tell us about a wave?

• Which of these waves would cause more damage if
  it hit the shore?
• Which has the larger amplitude?
• Which wave has more energy?

THATS AMPLITUDE!
12
Student s 5 and 6
Waves with _________________ amplitude have
more energy.

• Stretch the slinky out across the table.
• Student 5 Create two waves one with a large
  amplitude and one with a smaller one. Do not tell
  your group members which will be first and
  second.
• Everyone observe.
• Group members guess which wave had the larger
  amplitude.
• Student 6 Repeat and allow group members to
  guess which wave had the larger amplitude.

a larger
Which wave did you have to put more energy into
to create?
13
Weve been looking at transverse wavesWhat about
longitudinal?

• We can relate all of the parts of a transverse
  wave to a longitudinal one!

14
Well start with wavelength

• In a transverse wave
• But there arent any crests or troughs in a
  longitudinal wave!

The distance from crest to crest or trough to
trough
WAVELENGTH
WAVELENGTH
15
So we look at the compressions and rarefactions!

• Compressions Crests
• Rarefactions Troughs
• Now we can find the wavelength
• Compression to compression
• Rarefaction to rarefaction

16
Student s 7 and 8
Waves with _________________ wavelength have
more energy.

• Stretch the slinky out across the table.
• Student 7 You will be creating two longitudinal
  waves one with a large wavelength and one with a
  smaller one. Do not tell your group members which
  will be first and second.
• Everyone observe.
• Group members guess which wave had the larger
  wavelength.
• Student 8 Repeat and allow group members to
  guess which wave had the larger wavelength.

a shorter
Which wave did you have to put more effort into
creating?
17
On to amplitude

• In a transverse wave
• We now know that compressions are rarefactions
  are like the crests and troughs, but its hard to
  find a longitudinal waves resting point.

The distance from crest or trough to the wave's
resting point
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Amplitude

• For the amplitude of a longitudinal wave, we look
  at how compressed or how rarefied the spring or
  particles are.
• The more compressed or rarefied it is, the higher
  the amplitude and vice versa.

19
Student s 9 and 10 (or start back at 1)
Waves with _________________ amplitude have
more energy.

• Stretch the slinky out across the table.
• Student 9/1 Create two longitudinal waves one
  with a large amplitude and one with a smaller
  one. Do not tell your group members which will be
  first and second.
• Everyone observe.
• Group members guess which wave had the larger
  amplitude.
• Student 10/2 Repeat and allow group members to
  guess which wave had the larger amplitude.

a larger
Which wave did you have to put more energy into
to create?
20
Frequency

• If your friend comes over to your house
  frequently, how often do they come over?
• Can you take a guess as to what the frequency
  of a wave is?
• The frequency of a wave tells us the number of
  waves that are produced in a certain amount of
  time.

21
We need to know how many waves are being produced
in 10 seconds.

• How can you find the frequency of this wave?
• Step 1 pick a point on the wave.
• Step 2 count the waves that pass that point in
  10 seconds.

22
Which has a higher frequency?
23
Student s 1 or 3 and 2 or 4
Waves with _________________ frequency have
more energy.

• Stretch the slinky out across the table.
• Student 1/3 Create two waves one with a high
  frequency and one with a lower one. Try to keep
  the amplitudes the same in both waves. Do not
  tell your group members which will be first and
  second.
• Everyone observe.
• Group members guess which wave had the higher
  frequency.
• Student 2/4 Repeat and allow group members to
  guess which wave had the higher frequency.

a higher
Which wave did you have to put more energy into
to create?
24
What is the unit for frequency?

• Frequency is measured in Hertz (Hz).
• If one full wave passes a point every second, it
  has a frequency of 1 Hz.
• 1 wave per second (1 wave/1 sec.)
• What is the frequency if three waves pass a point
  every second?
• 3 Hz. (3 waves/1 second)
• What is the frequency if six waves pass a point
  every three seconds?
• 2 Hz. (6 waves/3 seconds)

25
Wave Speed

• There are two ways to calculate wave speed.
• Option 1 time how long a wave takes to get from
  point A to point B.

A
B
26

• Option 2 Use the following formula

Wave speed wavelength x frequency
Wave Speed 8 meters/second
Wavelength 2 meters
Frequency 4 Hz. (4 waves pass every second)
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• Wave speed is affected by several factors
• The type of wave
• Example electromagnetic waves always travel at
  the same speed in a vacuum (300,000 km/s the
  speed of light)
• The medium the wave is moving through
• If you start two waves in a pan, one with water
  and one with corn syrup, which will reach the
  other side of the pan first?
• Another example is popping your knuckles
  underwater as opposed to above water.