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## Waves

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### Ch 11 # 45 Types of Waves Longitudinal: The medium oscillates in the same direction as the wave is moving Sound ... of Waves on a string Example: guitar ... – PowerPoint PPT presentation

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Title: Waves

1
Waves
2
Types of Waves
8
3
Period and Velocity
22
4
• Suppose that a longitudinal wave moves along a
Slinky at a speed of 5 m/s. Does one coil of the
slinky move through a distance of five meters in
one second?
• 1. Yes
• 2. No

12
5
Harmonic Waves
Wavelength The distance ? between identical
points on the wave.
Amplitude The maximum displacement A of a point
on the wave.
Angular Frequency w w 2 p f
Wave Number k k 2 p / l
Recall f v / l
y
x
20
6
Example microwave
• The wavelength of microwaves generated by a
microwave oven is about 3 cm. At what frequency
do these waves cause the water molecules in your
burrito to vibrate ?

The speed of light is c 3x108 m/s
29
7
Interference and Superposition
• When too waves overlap, the amplitudes add.
• Constructive increases amplitude
• l2-l1 m ?
• Destructive decreases amplitude
• l2-l1 (m1/2) ?

34
8
Example two speakers
• Two speakers are separated by a distance of 5m
and are producing a monotone sound with a
wavelength of 3m. Other than in the middle,
where can you stand between the speakers and hear
constructive interference?

9
Example two speakers
• Two speakers are separated by a distance of 5m
and are producing a monotone sound with a
wavelength of 3m. Where can you stand between the
speakers and hear destructive interference?

10
Reflection Act
• A slinky is connected to a wall at one end. A
pulse travels to the right, hits the wall and is
reflected back to the left. The reflected wave is
• A) Inverted B) Upright
• Fixed boundary reflected wave inverted
• Free boundary reflected wave upright

37
11
Standing Waves Fixed Endpoints
• Fundamental n1
• ln 2L/n
• fn n v / (2L)

44
12
Velocity of Waves on a string
µ mass per unit length of string As µ
increases, v decreases, f decreases (? fixed)
17
13
Example guitar
A guitars E-string has a length of 65 cm and is
stretched to a tension of 82N. If it vibrates
with a fundamental frequency of 329.63 Hz, what
is the mass of the string?
48
14
Summary
• Wave Types
• Transverse (eg pulse on string, water)