Wave Model Terms and Wave Motion Principles

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Questions and Answers

Consider two waves traveling in the same medium. How does a change in wavelength of one wave affect its speed, assuming the medium remains constant?

  • Both waves will have the same speed regardless of their wavelengths. (correct)
  • The speed of the waves will vary non-linearly with the inverse square of the wavelength.
  • The wave with a longer wavelength will travel faster.
  • The wave with a shorter wavelength will travel faster.

A wave transitions from air into water. Which property of the wave remains unchanged during the transition?

  • Amplitude
  • Wavelength
  • Speed
  • Frequency (correct)

What is the relationship between the frequency ($f$) and the period ($T$) of a wave?

  • $f = \sqrt{T}$
  • $f = T$
  • $f = T^2$
  • $f = 1/T$ (correct)

Given a wave with a frequency of 5 Hz and a wavelength of 2 meters, what is the speed of the wave?

<p>10 m/s (D)</p> Signup and view all the answers

Which part of a transverse wave is characterized as the lowest point below its equilibrium position?

<p>Trough (C)</p> Signup and view all the answers

How is the wavelength ($\lambda$) defined in the context of a wave?

<p>The distance between two consecutive crests or troughs. (C)</p> Signup and view all the answers

If the frequency of a wave is doubled while it travels through the same medium, what happens to its wavelength?

<p>The wavelength is halved. (D)</p> Signup and view all the answers

Consider two waves, Wave A and Wave B, traveling through different media. Wave A has a higher speed than Wave B. Which of the following conclusions can be accurately drawn?

<p>The medium through which Wave A travels offers less resistance to wave propagation than the medium through which Wave B travels. (C)</p> Signup and view all the answers

How does increasing the frequency of a wave affect its properties upon entering a different medium, assuming the wave speed remains constant?

<p>The wavelength decreases proportionally to the frequency increase. (D)</p> Signup and view all the answers

If the amplitude of a wave is doubled and the frequency is halved, what is the resulting change in the wave's intensity?

<p>The intensity remains the same. (C)</p> Signup and view all the answers

A sound wave traveling through air has a period of 400 microseconds. What is the frequency of this wave?

<p>2.5 kHz (B)</p> Signup and view all the answers

What occurs when a transverse wave traveling in a denser medium is incident on a rarer medium?

<p>It is reflected without any change in phase. (D)</p> Signup and view all the answers

Given that the intensity of a wave is directly proportional to the square of its amplitude and frequency, how would you explain the relationship mathematically if 'k' is the proportionality constant?

<p>$I = k A^2 f^2$ (D)</p> Signup and view all the answers

Consider two waves with amplitudes A1 and A2. What condition must be met for their superposition to result in complete destructive interference at a point?

<p>A1 must be equal to A2 and they must be out of phase by $\pi$ radians. (D)</p> Signup and view all the answers

A transverse wave is reflected from a boundary. Under what conditions would the reflected wave undergo a phase shift of $\pi$ radians?

<p>When the wave travels from a rarer medium to a denser medium. (D)</p> Signup and view all the answers

If a wave's frequency is tripled while its speed remains constant, what happens to its period?

<p>The period is divided by three. (C)</p> Signup and view all the answers

A string with a linear mass density of $5.00 \times 10^{-3}$ kg/m is under a tension of 80.0 N. What is the speed of the wave produced in the string?

<p>40 m/s (C)</p> Signup and view all the answers

A stretched steel wire is 1 m long and has a fundamental frequency of 250 Hz. What is the velocity of the transverse wave in it?

<p>500 m/s (A)</p> Signup and view all the answers

How is the number of antinodes (N) related to the harmonic number (H) for standing waves?

<p>$N = H + 1$ (D)</p> Signup and view all the answers

What distinguishes the fundamental frequency from overtones in the context of waves?

<p>The fundamental frequency is the lowest frequency produced, while overtones are higher frequencies. (A)</p> Signup and view all the answers

A guitar string is vibrating at its third harmonic. If the length of the string is $L$, what is the distance between two consecutive nodes?

<p>$L/3$ (A)</p> Signup and view all the answers

Consider two strings of identical length and tension. String A has a linear mass density twice that of String B. What is the ratio of the fundamental frequency of String A to that of String B?

<p>$1/\sqrt{2}$ (C)</p> Signup and view all the answers

A string fixed at both ends vibrates in its fifth harmonic. At what points along the string (excluding the endpoints) can you touch the string without disturbing the standing wave?

<p>At points $L/5$, $2L/5$, $3L/5$, and $4L/5$ from one end, where $L$ is the length of the string. (D)</p> Signup and view all the answers

A standing wave is formed on a string of length $L$ fixed at both ends. If the frequency of the wave is doubled, which of the following is true about the new standing wave pattern?

<p>The number of antinodes is approximately doubled. (B)</p> Signup and view all the answers

In the context of sound wave interference, what condition primarily dictates whether the interference will be constructive or destructive?

<p>The relative phase of the waves at the point of interaction; in-phase waves lead to constructive interference, while those out-of-phase lead to destructive interference. (D)</p> Signup and view all the answers

What is the primary requirement for sound sources to be considered coherent in the context of interference?

<p>They must emit sound waves with identical and constant phase relationship. (C)</p> Signup and view all the answers

How does the path difference between two sound waves relate to the type of interference that occurs?

<p>A path difference equal to an integer multiple of the wavelength leads to constructive interference, while a path difference equal to an odd multiple of half the wavelength leads to destructive interference. (B)</p> Signup and view all the answers

In what scenario does a 'silence zone' typically occur in the context of sound wave interference?

<p>A silence zone arises in areas where sound waves from multiple sources destructively interfere, resulting in minimal sound intensity. (C)</p> Signup and view all the answers

What is the effect of destructive interference on the loudness and intensity of sound?

<p>Both the loudness and intensity of sound decrease due to the cancellation of waves. (B)</p> Signup and view all the answers

What occurs when the compression of one sound wave aligns with the rarefaction of another wave at a specific point?

<p>Destructive interference, leading to a reduced sound intensity at that point. (B)</p> Signup and view all the answers

Why is it essential for sound waves to travel in the same medium to observe interference effects?

<p>Different media can cause variations in wave speed and wavelength, disrupting the phase relationship needed for stable interference patterns. (B)</p> Signup and view all the answers

In the context of constructive sound interference, how does the resulting sound differ from the individual sounds that interfere?

<p>The resulting sound is louder, due to the increased amplitude from the reinforcement of the waves. (D)</p> Signup and view all the answers

Under what conditions does constructive interference of sound waves predominantly occur?

<p>When two identical waves meet at a point in phase, reinforcing each other to produce a larger amplitude. (C)</p> Signup and view all the answers

What is the fundamental principle that governs the superposition of waves in a medium?

<p>The total displacement at any point is the algebraic sum of the displacements of all individual waves. (D)</p> Signup and view all the answers

Consider $n$ waves acting simultaneously on a particle in a medium. If the displacement due to each wave is given by $y_i$, where $i$ ranges from 1 to $n$, what is the resultant displacement $Y$ of the particle?

<p>$Y = y_1 + y_2 + ... + y_n$ (C)</p> Signup and view all the answers

Two identical sound waves are propagating in the same direction through a medium. What phenomenon occurs when these waves 'mix up' or combine?

<p>Interference, resulting in the superposition of the waves. (D)</p> Signup and view all the answers

What happens to the energy of two waves that interfere destructively?

<p>The energy is redistributed in space, with some areas having increased energy and others decreased. (C)</p> Signup and view all the answers

How does the principle of superposition apply when analyzing complex soundscapes, such as in an orchestra?

<p>It enables the prediction of the combined sound wave by summing the individual sound waves, accounting for phase and amplitude. (C)</p> Signup and view all the answers

In the context of sound interference, what distinguishes 'identical' waves from similar waves with slightly different characteristics?

<p>Identical waves have the same frequency, amplitude, and phase relationship, whereas similar waves may differ in these properties. (D)</p> Signup and view all the answers

If two identical sound waves with amplitudes $A_1$ and $A_2$ interfere constructively at a point, and $A_1 = A_2 = A$, what is the amplitude of the resulting wave at that point?

<p>$2A$ (C)</p> Signup and view all the answers

Two identical sound waves, each with amplitude $A$, interfere in a medium. Under what conditions regarding their phase difference ($\phi$) will the resulting wave have an amplitude of $\frac{A}{2}$?

<p>$\phi = \arccos(\frac{3}{4})$ (A)</p> Signup and view all the answers

Consider two sound waves with amplitudes $A_1$ and $A_2$ interfering destructively. If the resulting amplitude is zero, what can be definitively concluded about the relationship between the initial waves at the point of interference?

<p>The waves have a phase difference of $\pi$ radians and $A_1 = A_2$. (C)</p> Signup and view all the answers

A string is fixed at both ends and supports a standing wave with three nodes (including the endpoints). If the length of the string is $L$, what is the wavelength of the standing wave?

<p>$L$ (D)</p> Signup and view all the answers

A pipe, open at both ends, has a fundamental frequency $f$. If one end of the pipe is closed, what is the new fundamental frequency, assuming the speed of sound remains constant?

<p>$\frac{1}{2}f$ (A)</p> Signup and view all the answers

The velocity of sound in air at a certain temperature is $v$. If the absolute temperature is doubled and the molar mass of the gas is quadrupled, what is the new velocity of sound?

<p>$\frac{v}{\sqrt{2}}$ (A)</p> Signup and view all the answers

Two speakers emit sound waves of the same frequency and amplitude. At a certain point, the sound intensity is four times what it would be from a single speaker alone. What is the phase difference between the waves at this point?

<p>$0$ radians (A)</p> Signup and view all the answers

A stationary wave is formed by the superposition of two waves, $y_1 = A\sin(kx - \omega t)$ and $y_2 = A\sin(kx + \omega t)$. What is the distance between two consecutive nodes in the resulting wave?

<p>$\frac{\lambda}{2}$ (B)</p> Signup and view all the answers

Consider a scenario where two identical sound sources are emitting waves in phase. At a certain point, the path difference to the listener is $\lambda/2$, where $\lambda$ is the wavelength. If the amplitude of each wave is $A$, what is the resulting amplitude at the listener's location?

<p>$0$ (D)</p> Signup and view all the answers

Flashcards

Constructive Interference

When two waves meet in phase, amplifying sound and increasing loudness.

Destructive Interference

When two waves meet out of phase, canceling each other, reducing sound intensity.

Conditions for Interference

Requires coherent sound sources, same frequency, and proximity of sources.

Echoing Zone

Region where constructive interference occurs, resulting in louder sounds.

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Silence Zone

Region where destructive interference occurs, leading to reduced sound intensity.

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Path Difference

The difference in distance traveled by two waves reaching the same point.

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Coherent Sources

Sound sources that maintain a constant phase relationship necessary for interference.

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Wave Medium

The material through which sound waves travel, influencing interference.

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Crest

The highest point of a wave above the equilibrium position.

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Trough

The lowest point of a wave below the equilibrium position.

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Wavelength

The distance between two consecutive crests or troughs of a wave.

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Wave Speed

The speed at which a wave crest travels through a medium.

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Frequency

The number of waves that pass a specific point in one second.

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Equilibrium Position

The central position of a wave where no disturbance occurs.

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Different Medium

When waves travel in different mediums, they retain their frequency but change speed.

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Wave Intensity

The power per unit area carried by a wave, proportional to the square of its amplitude and frequency.

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Amplitude

The maximum displacement from the rest position of a wave.

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Sound wave frequency

The frequency of a sound wave can be calculated using its period.

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Reflection of waves

When a wave strikes a medium, it can be reflected with or without a phase change depending on the medium's density.

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Transverse wave

A wave where the oscillation is perpendicular to the direction of the wave's travel.

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Phase Difference

The difference in phase between two waves at a specific point in time.

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Velocity of Sound

Speed at which sound waves travel through a medium, not affected by pressure changes.

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Temperature and Sound Velocity

Velocity of sound doubles with an increase in temperature; T2 = n*T1.

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Stationary Waves

Waves formed by the interference of two waves traveling in opposite directions, creating nodes and antinodes.

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Nodes and Antinodes

Points of no displacement (nodes) and maximum displacement (antinodes) in a wave pattern.

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Antinode

The point where the amplitude of standing waves is maximum.

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Harmonic Number

An integer representing the mode of vibration in a system.

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Fundamental Frequency

The lowest frequency of a periodic waveform; first harmonic.

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Overtone

Frequencies higher than the fundamental frequency.

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Linear Mass Density

Mass per unit length of a string, represented as m.

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Wave Speed Formula

The speed of a wave is represented as v = fλ (frequency times wavelength).

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Tension in a String

The force that stretches the string, influencing wave speed.

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Calculating Harmonic Number from Overtone

Use the relation: Harmonic number = Overtone number + 1.

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Total Displacement

The overall displacement at any point, resulting from multiple waves.

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Principle of Superposition

The principle stating that the total displacement is the sum of individual displacements caused by multiple waves.

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Interference of Sound

The phenomenon where sound waves overlap and combine while passing through the same medium.

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Identical Waves

Waves that have the same frequency and amplitude, traveling in the same direction.

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Resultant Displacement

The final displacement observed when multiple displacements from different waves combine.

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Medium in Sound Waves

The substance (air, water, etc.) through which sound waves travel.

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Study Notes

Learning Objectives

  • Define and apply wave model terms: medium, displacement, amplitude, period, compression, rarefaction, crest, trough, wavelength, and velocity.
  • Solve problems using the equation: v = fλ.
  • Describe energy transfer due to progressive waves.
  • Compare transverse and longitudinal waves.
  • Explain the factors affecting sound speed in a medium and describe Newton's formula, including the Laplace correction.
  • Identify factors influencing sound speed in air.
  • Describe superposition of waves from coherent sources.
  • Describe the phenomenon of sound wave interference.
  • Describe wave motion using ropes and springs.
  • Show that mechanical waves need a medium for propagation but electromagnetic waves do not.
  • Explain stationary waves graphically.
  • Define the terms node and antinode.
  • Describe string vibrations.
  • Describe stationary waves in vibrating air columns.
  • Explain the principle of superposition.
  • Explain Simple Harmonic Motion (SHM) and its characteristics.

Wave Speed

  • Wave speed can be measured by timing a wave crest's movement over a distance.
  • Wave speed is determined from frequency and wavelength (v = fλ).
  • In a single medium (like air or vacuum), waves of different frequencies have the same speed but different wavelengths.
  • In different mediums, the frequency remains the same, but the wavelength and speed change.

Intensity of a Wave

  • Intensity is directly proportional to the square of amplitude and frequency.

Reflection of Transverse Waves

  • Reflection occurs when a transverse wave encounters a denser medium with a 180° phase change.
  • Reflection occurs without a phase change when encountering a rarer medium.

Sound

  • Sound is a mechanical wave produced by a vibrating source.
  • Sound travels as longitudinal waves in mediums like air, water, and solids.
  • Sound waves result from compressions and rarefactions in the medium.

Wave Speed in a Medium

  • Speed of sound depends on the medium's elasticity and density:

Newton's Formula for Sound Speed

  • Newton calculated sound speed using the bulk modulus of elasticity and density.
  • The calculated value differed from experimental results.

Laplace's Correction

  • Laplace corrected Newton's formula, accounting for adiabatic processes in air, which significantly improves the result.

Audible Range

  • Humans hear frequencies between 20 Hz and 20,000 Hz.
  • Waves below 20 Hz are infrasonic, above 20,000 Hz are ultrasonic.

Doppler Effect

  • Doppler effect describes a change in the perceived frequency of a wave when the source or observer moves relative to each other.
  • The frequency increases if the source is moving towards the observer and decreases if moving away.
  • Similarly, an observer's motion towards or away from a stationary source also changes the perceived frequency.

Standing or Stationary Waves

  • When similar waves traveling in opposite directions combine, they form stationary waves.
  • These waves have points of zero displacement (nodes) and maximum displacement (antinodes).
  • The distance between successive nodes or antinodes is λ/2.
  • Stationary waves have alternating potential and kinetic energy as particles vibrate.

Organ Pipes

  • Organ pipes produce sounds due to stationary waves in air columns.
  • Open organ pipes have antinodes at both ends, resulting in certain frequencies.
  • Closed organ pipes have a node at one end and an antinode at the other, producing different frequencies

Standing Waves on a String

  • These waves show characteristic nodes and antinodes.
  • Their speed depends on string tension and linear density.

Combinations of Springs

  • Springs in series have an inverse relationship to their equivalent spring constant
  • Springs in parallel have an additive relationship to their equivalent spring constant

Simple Harmonic Motion (SHM)

  • SHM characteristics:
    • Acceleration is directly proportional to displacement.
    • Displacement is always directed towards a mean position.

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