11 Water waves are partially transverse and partially longitudinal.
12 In the drawing, one cycle is shaded in color. The amplitude A is the maximum excursion of a particle of the medium fromthe particles undisturbed position.The wavelength is the horizontal length of one cycle of the wave.The period is the time required for one complete cycle.The frequency is related to the period and has units of Hz, or s-1.
14 The Wavelengths of Radio Waves AM and FM radio waves are transverse waves consisting of electric andmagnetic field disturbances traveling at a speed of 3.00x108m/s. A stationbroadcasts AM radio waves whose frequency is 1230x103Hz and an FMradio wave whose frequency is 91.9x106Hz. Find the distance betweenadjacent crests in each wave.
25 Transverse waves travel on each string of an electric guitar after the string is plucked. The length of each string between its two fixed endsis m, and the mass is g for the highest pitched E string and3.32 g for the lowest pitched E string. Each string is under a tensionof 226 N. Find the speeds of the waves on the two strings.
27 The distance between adjacent condensations is equal to the wavelength of the sound wave.
28 Individual air molecules are not carried along with the wave.
29 THE FREQUENCY OF A SOUND WAVE The frequency is the number of cyclesper second.A sound with a single frequency is calleda pure tone.The brain interprets the frequency in termsof the subjective quality called pitch.
30 THE PRESSURE AMPLITUDE OF A SOUND WAVE Loudness is an attribute ofa sound that depends primarilyon the pressure amplitudeof the wave.
31 Sound travels through gases, liquids, and solids at considerably 16.6 The Speed of SoundSound travels through gases,liquids, and solids at considerablydifferent speeds.
32 In a gas, it is only when molecules collide that the condensations and 16.6 The Speed of SoundIn a gas, it is only when molecules collide that the condensations andrerefactions of a sound wave can move from place to place.Ideal Gas
33 Conceptual Example 5 Lightning, Thunder, and a Rule of Thumb 16.6 The Speed of SoundConceptual Example 5 Lightning, Thunder, and a Rule of ThumbThere is a rule of thumb for estimating how far away a thunderstorm is.After you see a flash of lighting, count off the seconds until the thunderis heard. Divide the number of seconds by five. The result gives theapproximate distance (in miles) to the thunderstorm. Why does thisrule work?
35 Sound waves carry energy that can be used to do work. 16.7 Sound IntensitySound waves carry energy that can be used to do work.The amount of energy transported per second is called thepower of the wave.The sound intensity is defined as the power that passes perpendicularlythrough a surface divided by the area of that surface.
36 Example 6 Sound Intensities 16.7 Sound IntensityExample 6 Sound Intensities12x10-5W of sound power passed through the surfaces labeled 1 and 2. Theareas of these surfaces are 4.0m2 and 12m2. Determine the sound intensityat each surface.
38 For a 1000 Hz tone, the smallest sound intensity that the human ear can detect is about 1x10-12W/m2. This intensity is called the thresholdof hearing.On the other extreme, continuous exposure to intensities greater than1W/m2 can be painful.If the source emits sound uniformly in all directions, the intensity dependson the distance from the source in a simple way.
39 16.7 Sound Intensitypower of sound sourcearea of sphere
40 Conceptual Example 8 Reflected Sound and Sound Intensity Suppose the person singing in the shower produces a sound power P.Sound reflects from the surrounding shower stall. At a distance r in frontof the person, does the equation for the intensity of sound emitted uniformlyin all directions underestimate, overestimate, or give the correct soundintensity?
41 The decibel (dB) is a measurement unit used when comparing two sound 16.8 DecibelsThe decibel (dB) is a measurement unit used when comparing two soundintensities.Because of the way in which the human hearing mechanism responds tointensity, it is appropriate to use a logarithmic scale called the intensitylevel:Note that log(1)=0, so when the intensityof the sound is equal to the threshold ofhearing, the intensity level is zero.
43 Example 9 Comparing Sound Intensities 16.8 DecibelsExample 9 Comparing Sound IntensitiesAudio system 1 produces a sound intensity level of 90.0 dB, and system2 produces an intensity level of 93.0 dB. Determine the ratio of intensities.
45 The Doppler effect is the change in frequency or pitch of the sound detected byan observer because the soundsource and the observer havedifferent velocities with respectto the medium of soundpropagation.
47 16.9 The Doppler Effectsource movingtoward a stationaryobserversource movingaway from a stationaryobserver
48 Example 10 The Sound of a Passing Train 16.9 The Doppler EffectExample 10 The Sound of a Passing TrainA high-speed train is traveling at a speed of 44.7 m/s when the engineersounds the 415-Hz warning horn. The speed of sound is 343 m/s. Whatare the frequency and wavelength of the sound, as perceived by a personstanding at the crossing, when the train is (a) approaching and (b) leavingthe crossing?
51 16.9 The Doppler EffectObserver movingtowards stationarysourceObserver movingaway fromstationary source
52 Numerator: plus sign applies when observer moves towards the source 16.9 The Doppler EffectGENERAL CASENumerator: plus sign applieswhen observer moves towardsthe sourceDenominator: minus sign applieswhen source moves towardsthe observer
53 16.10 Applications of Sound in Medicine By scanning ultrasonic waves across the body and detecting the echoesfrom various locations, it is possible to obtain an image.
54 16.10 Applications of Sound in Medicine Ultrasonic sound waves causethe tip of the probe to vibrate at23 kHz and shatter sections ofthe tumor that it touches.
55 16.10 Applications of Sound in Medicine When the sound is reflectedfrom the red blood cells, itsfrequency is changed in akind of Doppler effect becausethe cells are moving.