1. Frequency and Types of Waves

2. Review: Features of a Wave
A crest is the highest point on a wave.
A trough is the lowest point on a wave.
The wavelength is the distance, in meters, for one complete cycle of the wave.
Crest to crest or trough to trough.
The amplitude is the height of a wave crest or depth of a trough, as measured from its rest position.
See pages
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3. Activity
Catch a Wave Form p139

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Frequency
Frequency is the number of repetitive motions, or oscillations, that occur in a given time.
Frequency is usually measured in hertz (Hz).
When the frequency of a wave increases the wavelength decreases.
This is called an Inverse Relationship.
This is called an Inverse Relationship
See page 136
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Bill Nye: Waves
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6. Calculating Frequency
Frequency can be calculated using the following equation:
frequency = cycles/seconds
Use the above equation to find the frequency for each of the following:
a) A hummingbird flaps its wings 120 times in 3 seconds.
b) A DVD spins 35 times in 7 seconds.
Go to the next slide to view the answers
See page 138
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7. Calculating Frequency
Frequency can be calculated using the following equation:
frequency = cycles/seconds
Use the above equation to find the frequency for each of the following:
a) A hummingbird flaps its wings 120 times in 3 seconds.
(40 Hz)
b) A DVD spins 35 times in 7 seconds. (5 Hz)
Take the Section 4.1 Quiz
See page 138
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8. Waves Travel through different mediums
The matter that waves travel through is called a medium (can be solid, liquid, gas)
Some waves such as light waves, can travel through space where there is no medium.
See page 137
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Two Types of Waves
Two types of waves that travel through a medium are:
Transverse wave – matter in the medium moves perpendicular to direction of the wave. All types of electromagnetic radiation, including visible light, are transverse waves waves.  .
Transverse wave
See page 137
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Two Types of Waves
Compression wave – matter in the medium moves parallel to direction of the wave.
Eg. sound waves (vibrations in pressure, and seismic P- waves (created by earthquakes and explosions).
Compression wave
See page 137
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Summary
Waves transfer energy through matter or space.
Amplitude is the height of a waves crest or depth of a wave trough, as measured from its rest position.
A wavelength is the distance over which the wave repeats.
As the wavelength decrease, the frequency increases.
Waves can differ in how much energy they carry and in how fast they travel.
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Practice
Read pages
Calculating Frequency WS – due at the end of class
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Practice
Homework
Read pages
Answer CYU p143 #1, 2, 3, 4, 7, 8.
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