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Waves and Sound

Wave Vocabulary. Wave: a traveling disturbance carrying energy from one place to another.Transverse wave: here the disturbance moves perpendicular to the direction of wave motion. (Example: wave on a string)Longitudinal wave: here the disturbance moves parallel to the direction of wave mot

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Waves and Sound

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    1. Waves and Sound Chapter 16

    2. Wave Vocabulary There is no bulk motion of the wave, each particle just moves up and down or left and right!There is no bulk motion of the wave, each particle just moves up and down or left and right!

    3. More Wave Vocabulary Note: wave velocity is not velocity of each individual point! Fig 16.6Note: wave velocity is not velocity of each individual point! Fig 16.6

    4. Speed, Wavelength, and Frequency

    5. Example f = 1200 kHz = 1,200,000 Hz v = 3 x 108 m/s lambda = v / f =300,000,000 m/s / 1,200,000 Hz =250 mf = 1200 kHz = 1,200,000 Hz v = 3 x 108 m/s lambda = v / f =300,000,000 m/s / 1,200,000 Hz =250 m

    6. Speed in a String

    7. Speed in a String m/L is density big T, big a small den, big a Note: vel of wave, not particle! demo with M-90m/L is density big T, big a small den, big a Note: vel of wave, not particle! demo with M-90

    8. Example Draw: A(top) taller and shorter wavelength B(bottom) (a) A (b) A (c) B (d) BDraw: A(top) taller and shorter wavelength B(bottom) (a) A (b) A (c) B (d) B

    9. Sound Vocabulary There is no bulk motion of the wave, each particle just moves up and down or left and right! Not like wind! Fig 16.14 M-92 again.There is no bulk motion of the wave, each particle just moves up and down or left and right! Not like wind! Fig 16.14 M-92 again.

    10. Sound Ranges

    11. Pitch

    12. Loudness

    13. The Speed of Sound Have formulas in book that calculate this exactly, will not cover in class, but will use for a conceptual problem.Have formulas in book that calculate this exactly, will not cover in class, but will use for a conceptual problem.

    14. Thunder and Lightning v (light) = 300000000 m/s v (sound) = 343 m/s (light is just about instantaneous) one mile = 1.6 x 10 3 m v = del(x) / t t = del(x) / v = 1.6 x 103 m / 343 m/s = 5 sec so for every 5 sec, the lightning is 1 mile away.v (light) = 300000000 m/s v (sound) = 343 m/s (light is just about instantaneous) one mile = 1.6 x 10 3 m v = del(x) / t t = del(x) / v = 1.6 x 103 m / 343 m/s = 5 sec so for every 5 sec, the lightning is 1 mile away.

    15. The Doppler Effect Fig 16.32Fig 16.32

    16. The Doppler Effect Fig 16.32 observed wavelength changesFig 16.32 observed wavelength changes

    17. The Doppler Effect write: f ==> frequency perceived by observer f==> freq emitted by source vs ==> velocity of source, v ==> velocity of soundwrite: f ==> frequency perceived by observer f==> freq emitted by source vs ==> velocity of source, v ==> velocity of sound

    18. Example v = 343 m/s (a) approaching, so minus f = f(1/ 1-vs/v) = (415 hz) ( 1/ 1 - 44.6m/s / 343) f = 477 HZ --> higher, as we expect (b) receding, so plus f = f(1/ 1+vs/v) = (415 hz) ( 1/ 1 + 44.6m/s / 343) f = 367 Hz --> lower, as we expect also, bigger speed, more effect!!!v = 343 m/s (a) approaching, so minus f = f(1/ 1-vs/v) = (415 hz) ( 1/ 1 - 44.6m/s / 343) f = 477 HZ --> higher, as we expect (b) receding, so plus f = f(1/ 1+vs/v) = (415 hz) ( 1/ 1 + 44.6m/s / 343) f = 367 Hz --> lower, as we expect also, bigger speed, more effect!!!

    19. The Doppler Effect Fig 16.34 here the frequency changes!! (wavelength is still same, but interpreted speed is increased) v=f lambda lambda = v/fFig 16.34 here the frequency changes!! (wavelength is still same, but interpreted speed is increased) v=f lambda lambda = v/f

    20. The Doppler Effect write: f ==> frequency perceived by observer f==> freq emitted by source vo ==> velocity of observer, v ==> velocity of soundwrite: f ==> frequency perceived by observer f==> freq emitted by source vo ==> velocity of observer, v ==> velocity of sound

    21. Example (a) source is approaching, so (wavelength is shorter) and frequency is higher than stationary (b) listener is approaching, so the frequency is higher than stationary(a) source is approaching, so (wavelength is shorter) and frequency is higher than stationary (b) listener is approaching, so the frequency is higher than stationary

    22. Example train A: moving faster train B: moving slower from As point of view, its approaching the source (train B) at a high speed --> smaller wavelength, so bigger frequency (higher pitch) from train Bs point of view, its approaching the source (train A) at a high speed -- the same speed! its the relative speeds that mattertrain A: moving faster train B: moving slower from As point of view, its approaching the source (train B) at a high speed --> smaller wavelength, so bigger frequency (higher pitch) from train Bs point of view, its approaching the source (train A) at a high speed -- the same speed! its the relative speeds that matter

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