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
Frequency = 1/Period
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) X (Wavelength) or 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,
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 (e.g. page 327).
3. Study each picture in the chapters and read their captions.
4. Reread the chapters.