Review Concepts for Exam I

Chapter 19 - Vibrations and Waves

Sine Curve - a wave form traced by simple harmonic motion

Amplitude - the distance of maximum displacement from the equilibrium position

Wavelength - the distance between successive crests

Frequency - the number of vibrations per unit time; measured in Hertz

The frequency of a wave depends only on the source of vibration.

Period - the time required for one vibration

Wave Speed - the speed with which a wave passes a stationary point

The wave speed depends only on the type of medium. Wave Speed = Frequency Wavelength. v=fl

Transverse Wave - a wave in which the medium moves perpendicular to the direction in which the wave travels

Longitudinal Wave - a wave in which the medium moves parallel to the direction in which the wave travels

Interference Pattern - a pattern formed by the addition of two waves

Interference of waves can result in constructive or destructive interference.

Standing Wave - a stationary wave pattern formed when identical waves pass through a medium in opposite directions

Demonstrations: standing waves on a rope, in an organ pipe, on a metal plate with salt

Doppler Effect - the change in frequency of a wave due to the motion of the sender or receiver

Bow Wave - a V-shaped wave behind a boat that forms when the boat travels faster than the speed of water waves

Shock Wave - a cone-shaped wave behind a plane that forms when the plane travels faster than the speed of sound

Sonic Boom - the loud (boom-boom) sound resulting from a shock wave hitting your ear

The crack of a whip is a small sonic boom.

Chapter 20 - Sound

Speed of Sound: depends only on the medium; for air the speed of sound is 340 m/s=760 miles/hour = Mach 1

Sound requires a Medium: Gas, Liquid, or Solid

Demonstration: buzzer in an evacuated bell jar

At an interface between two media sound waves are reflected, transmitted and absorbed.

Infrasonic - sound waves with frequencies below 20 Hertz

Audible - sound waves with frequencies between 20 Hertz and 20,000 Hertz

Ultrasonic - sound waves with frequencies greater that 20,000 Hertz

Demonstration: a speaker with frequency generator

Compression - a condensed region of a medium through which a longitudinal wave travels

Rarefaction - a rarefied region of a medium through which a longitudinal wave travels

Reverberation - the garbled sound that results from multiple reflections of sound waves; re-echoed sound

Refraction - the bending of a wave through a non-uniform medium, caused by difference in wave speeds

Sound waves bend toward cooler air.

Forced Vibrations - the setting up of vibrations in an object by a vibrating force

Demonstration: touching a tuning fork to a table top

Natural Frequency - a frequency at which an elastic object naturally tends to vibrate

Demonstration: dropping aluminum rods of different lengths

Resonance - the result of a forced vibration in a body when the applied frequency matches the

natural frequency of the body; high amplitude vibrations occur during resonance

Demonstrations: breaking a wine glass, Tacoma Narrows Bridge

Beats - the throbbing sound heard when two slightly different tones are played together

The beat frequency is simply the difference in the frequencies of the two tones.

Carrier Wave - a high frequency radio wave that "carries" a sound wave through a process called modulation

Modulation - impressing one wave system (sound wave) upon another of a higher frequency (radio waves)

Types of Modulation: Amplitude Modulation (AM), Frequency Modulation (FM)

Chapter 21 - Musical Sounds

Pitch - the "highness" or "lowness" of a tone; corresponds to the frequency of a sound

Loudness - the physical sensation directly related to the sound intensity; measured in decibels

Quality - the characteristic of a sound that allows us to distinguish between the same tone

played by different musical instruments

Quality is governed by the number and relative amplitudes of partial tones.

Partial Tone - one of the frequencies present in a complex tone

Fundamental Frequency - the lowest frequency of vibration; the first harmonic

Demonstration: In a string the fundamental frequency makes a single segment or loop.

Harmonic - a partial tone that is and integer multiple of the fundamental

Demonstrations: guitar string, organ pipe, rotating plastic tube

Musical Scale - a succession of notes of frequencies that are in simple ratios to one another

Fourier Analysis - a mathematical method of that will resolve a complex sound wave into a series of partial tones

How to Study

1. Review homework questions.

2. Review the Summary of Terms section at the end of each chapter.

2. Review the questions in blue throughout the chapters.

3. Study each picture in the chapters and read their captions.

4. Reread the chapters.