Chapter 20 : Traveling Waves 20.1 The wave model 20.2 - - PowerPoint PPT Presentation

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Chapter 20 : Traveling Waves 20.1 The wave model 20.2 - - PowerPoint PPT Presentation

Feb 06, 2024 105 likes •242 views

Chapter 20 : Traveling Waves 20.1 The wave model 20.2 One-dimensional waves 20.3 Sinusoidal waves 20.4 Waves in 2- & 3-dimensions 20.5 Sound and Light Waves 20.6 Power and Intensity 20.7 Doppler Effect What is the essence of waviness? 1

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Chapter 20: Traveling Waves 20.1 The wave model 20.2 One-dimensional waves 20.3 Sinusoidal waves 20.4 Waves in 2- & 3-dimensions 20.5 Sound and Light Waves 20.6 Power and Intensity 20.7 Doppler Effect

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What is the essence of waviness?

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The Wave Model

What is a wave? … a disturbance that moves through a medium (or vacuum). Types of waves:

  • 1. Mechanical waves: water waves and sound waves
  • 2. Electromagnetic waves: light waves including radio waves, x-rays, etc
  • 3. Matter waves: electrons and atoms show wave-like characteristics

Wave

Continuous, nonlocalized, collective

Particles

discrete, localized, individual 4

Waves: examples

  • 1. Ripples on a pond …

Think of a leaf, or a cork on the water … … this leaf (or water) “bobs” up and down, but the disturbance, i. e. the ripples, moves to the edge of the pond.

  • 2. Slinky …

the disturbance, red-dot moves back and forth…, but the wave moves from one end to the other. A wave transfers energy, but no material or substance from the source.

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Waves: examples

  • 3. Cornfield…

As the wind blows across the field, observe one stalk ...the disturbance, ear of corn, moves side to side, but the wave across the field.

  • 4. Waves on a string or a rope- example of one dimensional waves

up/down motion of wave at speed v

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Waves on a string

Wave speed: v = √ √ √ √Ts/µ µ µ µ Ts = tension, µ µ µ µ = linear density = mass/length Does v depend on size of the wave?

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Wave speed, wavelength, time period and frequency t Wavelength = distance from one crest to the next Frequency (f) = number of cycles (ups and downs) per second Period = time for one complete cycle (up-down-up) = 1/f Amplitude = Height of a crest Speed (v) = wavelength/period = frequency x wavelength

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Two types of wave motion: transverse and longitudinal Transverse waves: … the disturbance is perpendicular to the direction of the wave. Examples? Longitudinal waves: …the disturbance is parallel to the wave. slinky Sound wave, speed = 1100ft/s (approx)

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Electromagnetic spectrum

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Chapter 20. Reading Quizzes

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A graph showing wave displacement versus position at a specific instant of time is called a

  • A. snapshot graph.
  • B. history graph.
  • C. bar graph.
  • D. line graph.
  • E. composite graph.

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A graph showing wave displacement versus position at a specific instant of time is called a

  • A. snapshot graph.
  • B. history graph.
  • C. bar graph.
  • D. line graph.
  • E. composite graph.
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A graph showing wave displacement versus time at a specific point in space is called a

  • A. snapshot graph.
  • B. history graph.
  • C. bar graph.
  • D. line graph.
  • E. composite graph.

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A graph showing wave displacement versus time at a specific point in space is called a

  • A. snapshot graph.
  • B. history graph.
  • C. bar graph.
  • D. line graph.
  • E. composite graph.

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A wave front diagram shows

  • A. the wavelengths of a wave.
  • B. the crests of a wave.
  • C. how the wave looks as it moves

toward you.

  • D. the forces acting on a string that’s

under tension.

  • E. Wave front diagrams were not

discussed in this chapter.

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A wave front diagram shows

  • A. the wavelengths of a wave.
  • B. the crests of a wave.
  • C. how the wave looks as it moves

toward you.

  • D. the forces acting on a string that’s

under tension.

  • E. Wave front diagrams were not

discussed in this chapter.

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The waves analyzed in this chapter are

  • A. string waves.
  • B. sound and light waves.
  • C. sound and water waves.
  • D. string, sound, and light waves.
  • E. string, water, sound, and light waves.

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The waves analyzed in this chapter are

  • A. string waves.
  • B. sound and light waves.
  • C. sound and water waves.
  • D. string, sound, and light waves.
  • E. string, water, sound, and light waves.

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Sine-function: mathematical representation of a wave

x ( ) sin 2 x E x E π ϕ π ϕ π ϕ π ϕ λ λ λ λ

  • =

+ = + = + = +

  • λ

λ λ λ 2λ λ λ λ 3λ λ λ λ ( ) E x E

Amplitude Amplitude Phase (initial)

ϕ ϕ ϕ ϕ = = = =

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Sinusoidal Waves are periodic both in time and space

Source of the Wave Time Distribution of waves in space at different time

x

v

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Phase difference Phase = Phase difference:

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Waves in Two and Three Dimensions

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Power and Intensity Power (P) = the rate of energy transfer from the source (J/sec) Intensity = P/area = Power-to-area ratio ∝ ∝ ∝ ∝ Amplitude2 Sound intensity level:

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Doppler Effect: observed frequency shift due to motion

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Doppler Effect …

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Doppler Effect …

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EXAMPLE 20.11 How fast are the police traveling?

QUESTION:

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EXAMPLE 20.11 How fast are the police traveling?

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EXAMPLE 20.11 How fast are the police traveling?

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Chapter 20. Summary Slides Chapter 20. Summary Slides

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General Principles

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General Principles

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Important Concepts

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Important Concepts

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Applications

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Applications

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Applications

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Chapter 20. Multiple Chapter 20. Multiple-

  • Choice

Choice Questions Questions

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Which of the following actions would make a pulse travel faster down a stretched string?

  • A. Use a heavier string of the same length,

under the same tension.

  • B. Use a lighter string of the same length,

under the same tension.

  • C. Move your hand up and down more

quickly as you generate the pulse.

  • D. Move your hand up and down a larger

distance as you generate the pulse.

  • E. Use a longer string of the same thickness,

density, and tension.

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Which of the following actions would make a pulse travel faster down a stretched string?

  • A. Use a heavier string of the same length,

under the same tension.

  • B. Use a lighter string of the same length,

under the same tension.

  • C. Move your hand up and down more

quickly as you generate the pulse.

  • D. Move your hand up and down a larger

distance as you generate the pulse.

  • E. Use a longer string of the same thickness,

density, and tension.

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What is the frequency of this traveling wave?

  • A. 0.1 Hz
  • B. 0.2 Hz
  • C. 2 Hz
  • D. 5 Hz
  • E. 10 Hz

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  • A. 0.1 Hz
  • B. 0.2 Hz
  • C. 2 Hz
  • D. 5 Hz
  • E. 10 Hz

What is the frequency of this traveling wave?

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What is the phase difference between the crest of a wave and the adjacent trough?

  • A. 0

B.

  • C. /4
  • D. /2
  • E. 3 /2

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What is the phase difference between the crest of a wave and the adjacent trough?

  • A. 0

B.

  • C. /4
  • D. /2
  • E. 3 /2
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A light wave travels through three transparent materials of equal thickness. Rank in order, from the largest to smallest, the indices of refraction n1, n2, and n3.

  • A. n1 > n2 > n3
  • B. n2 > n1 > n3
  • C. n3 > n1 > n2
  • D. n3 > n2 > n1
  • E. n1 = n2 = n3

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A light wave travels through three transparent materials of equal thickness. Rank in order, from the largest to smallest, the indices of refraction n1, n2, and n3.

  • A. n1 > n2 > n3
  • B. n2 > n1 > n3
  • C. n3 > n1 > n2
  • D. n3 > n2 > n1
  • E. n1 = n2 = n3

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Amy and Zack are both listening to the source of sound waves that is moving to the right. Compare the frequencies each hears.

  • A. fAmy > fZack
  • B. fAmy < fZack
  • C. fAmy = fZack

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Amy and Zack are both listening to the source of sound waves that is moving to the right. Compare the frequencies each hears.

  • A. fAmy > fZack
  • B. fAmy < fZack
  • C. fAmy = fZack