Physics Chapter 12: Mechanical Waves

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Questions and Answers

How does increasing the tension in a string affect the wave speed?

Wave speed becomes unpredictable.

Wave speed decreases.

Wave speed increases. (correct)

Wave speed remains unchanged.

Which factor does NOT influence the speed of sound in a gas?

Temperature of the gas.

Molecular mass of the gas.

Density of the gas.

Pressure of the gas. (correct)

At a constant temperature, how does the molecular mass of a gas affect the speed of sound?

Speed of sound decreases with decreasing molecular mass.

Speed of sound is independent of molecular mass.

Speed of sound increases with increasing molecular mass.

Speed of sound increases with decreasing molecular mass. (correct)

What happens to the speed of sound as the temperature of the medium increases?

Speed of sound increases. Signup and view all the answers

Which of the following holds true for wave speed in different mediums?

Sound travels faster in liquids than in gases. Signup and view all the answers

What is the relationship between linear density and wave speed in a string?

Increasing linear density decreases wave speed. Signup and view all the answers

What is the speed of sound in air at 20°C?

343 m/s Signup and view all the answers

Which property primarily determines the speed of a wave in a tensioned string?

The string's mass-to-length ratio. Signup and view all the answers

How do particles in a transverse wave behave?

They oscillate vertically while the wave travels horizontally. Signup and view all the answers

Which type of wave is known to be faster?

P waves Signup and view all the answers

What is a characteristic of matter waves?

They describe the wave-like behavior of material particles. Signup and view all the answers

What happens to the wave speed in materials as the temperature increases?

Wave speed increases with temperature. Signup and view all the answers

Which of the following waves is considered more destructive during an earthquake?

S waves Signup and view all the answers

Which type of wave demonstrates particle motion that is parallel to the wave direction?

Longitudinal waves Signup and view all the answers

Which type of wave travels faster and is commonly associated with seismic activity?

P waves Signup and view all the answers

What factor does NOT affect the speed of a wave in a medium?

Color of the medium Signup and view all the answers

How does an increase in air temperature affect the speed of a sound wave?

It increases the speed Signup and view all the answers

For a wave traveling on a string, what happens when the tension is increased?

The speed of the wave increases Signup and view all the answers

Which of the following statements about wave speed in different mediums is true?

A 400-Hz sound wave travels faster in oil than in air Signup and view all the answers

If a speaker emits a 400-Hz tone and the air temperature rises, what happens to the wavelength of the sound?

The wavelength increases Signup and view all the answers

What is the relationship between wave speed, wavelength, and frequency for a sinusoidal wave?

$v = \lambda \cdot f$ Signup and view all the answers

In what way does wavelength change when moving from air to water for a sound wave of constant frequency?

Wavelength increases in water Signup and view all the answers

What describes the motion of particles in a medium as a sinusoidal wave travels through it?

Simple harmonic motion Signup and view all the answers

Study Notes

Chapter 12 Lecture Topics

The lecture covers mechanical waves, periodic mechanical waves, wave speeds, and the mathematical description of a wave.
Additional topics include reflections, superposition, standing waves, normal modes, longitudinal standing waves, interference, sound, hearing, sound intensity, beats, and the Doppler effect.
The goals of the chapter include describing mechanical waves, understanding superposition, standing waves, and sound, presenting sound as a standing longitudinal wave, demonstrating wave interference, studying sound intensity and beats, solving for frequency shifts (Doppler effect), and examining applications of acoustics and musical tones.
Mechanical waves involve the motion of a substance (medium) through which they move.
A wave is an organized disturbance that travels with a defined wave speed.
Waves transfer energy, but not matter.
Electromagnetic waves (EM waves) include visible light, radio waves, microwaves, and x-rays; they don’t require a medium to travel.
Matter waves describe the wave-like characteristics of material particles at an atomic scale.

Types of Mechanical Waves

Transverse waves: particle motion is perpendicular to wave motion (e.g., a wave on a string).
Longitudinal waves: particle motion is parallel to wave motion (e.g., sound waves).
Water waves are a complex mix of both transverse and longitudinal motions.
Earthquake waves are important examples of both transverse (S waves) and longitudinal (P waves).

Wave Speed

Wave speed depends on the properties of the medium, not the properties of the wave.
For strings, wave speed is determined by tension and linear density (mass per unit length).
Higher tension typically means higher wave speed; higher linear density means lower wave speed.
Sound wave speed in a gas is affected by temperature and molecular mass.
Warmer temperature and lower molecular mass typically increase wave speed.
Wave speed in liquids and solids is generally faster than in gases.
The speed of electromagnetic waves (e.g., light) in a vacuum is a constant (approximately 3.00 × 10⁸ m/s).

Mathematical and Graphical Descriptions

A snapshot graph shows displacement as a function of position at a single time.
A history graph shows displacement as a function of time at a single position.
Sinusoidal waves have a repeating pattern; their displacement can be described mathematically.
Important relationships include:
v = λf
the speed of the wave equals the wavelength multiplied by the frequency.

Other Concepts

Wave reflections can occur at boundaries, causing inversions or no inversions depending on the boundary conditions.
Wave superposition describes how waves interact when they overlap; this can result in constructive interference, destructive interference, or a complex pattern.
Standing waves occur when waves interfere to create a pattern of nodes (no motion) and antinodes (maximum motion).
Different resonant patterns may occur when the length of the medium or cavity is restricted in various ways

Additional Examples

Worked examples are available in the text (pages).
Examples include how long it takes for a spider to detect an insect landing on its web, calculating the speed of a wave on a string, determining the fundamental frequencies for various sounds, determining the velocity of sound, and sound intensity (decibel levels).

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Description

This quiz explores the fundamental concepts of mechanical waves, including their properties, behavior, and applications. Topics such as wave speed, reflection, interference, sound intensity, and the Doppler effect are covered. Test your understanding of how waves transfer energy and their mathematical descriptions.