Waves and Sound Review Name ___________ _

Waves-General Vocabulary: crest, trough, wavelength, period, fi'equency, pitch, amplitude, node, anti-node, transverse wave,

longitudinal wave, standing wave, compression, rarefaction, infrasonic, ultrasonic, resonance, harmonics, Doppler Effect, red shift, shock wave, constructive interference, destructive interference

Frequency (I) = # waves/time (unit = IIsec = hertz)

Period (T) = time for one wave cycle (unit = seconds) T = IIf

Types of waves: Transverse: water waves, S-waves in em1hquakes Longitudinal: sound waves, P-waves in earthquakes

Law of Snperposition: During interference, the amplitudes of2 or more waves add together Constrnctive Interference: crests add to crests, and troughs add to troughs, increasing the amplitude Destructive Interference: crests add to troughs, decreasing the amplitude

Energy of a wave: amplitude measures the amount of energy in a wave

Wave Speed = wavelength x frequency (unit = m/sec) velocity = i1p/i1t (distance traveled/travel time) (unit = m/sec). Denser media = faster wave speed Tension: increasing the tension in a medium will increase the wave speed (i.e. guitar string)

Standing Waves: created when incident and reflected waves interfere to make stable patterns of constructive and destructive interference. The higher the fi'equency, the more nodes will be created (shorter wavelength) In strings: Nodes must be located at the end points. In tubes: displacement anti-nodes will be at open ends of the tube, nodes will be at closed ends.

Speed of waves in various media • Waves need a medium. • Waves travel at a measurable speed (speed is fixed for a specific medium). • Waves travel fastest and best (lose less energy) through denser media

Doppler Effect: the change in frequency caused by moving wave source or an observer moving relative to a wave source. The fi'equency of a wave is increased in front of a moving wave source, and decreased behind the wave source. Example: The sound ofa car engine passing you sounds higher as it approaches you, and lower as·it moves away fi'om you. The actual pitch of the car engine is in between the high and low pitch (you hear this pitch for the very brieftime that the car is right alongside you).

Sound Waves Sound -- General

• Sound sources are vibrating objects. • Standing waves create continuous sounds (vibrating tuning fork, wine glass, etc) • Sound travels away from source. • Sound waves are longitudinal waves and create a series of compressions and rarefactions (expansions) • The size and properties of the vibrating object affect the sound produced. • While sound is a longitudinal wave, it's often represented as a transverse wave because it's easier to draw. • Our perception of sound is related to the sound waves properties: frequency - pitch, amplitude - loudness, complexity - quality/tone

Frequency and Pitch • The faster the frequency, the lower the wave length, the hi gher the pi tch. • The frequency created by an object depends on that objects compos ition, density, tension, and length. • The pitch of a sound can be mani pulated using the things listed above. Music.is made this way. • Notes on in struments are created by standin g waves in the obj ect produc in g the sound .

Resonance and Harmonics • Everything has a natural vibrat ing frequ ency. Somethin g vibrat ing at thi s frequency has resonance. • Objects can al so have forced vibrations. (tuning fork making a table top v ibrate w ith the same frequency) • The amplitude o f an object's vibrations can be increased if the vibrations o f another object matches the natura l frequency o f the first object. Examples : Tuning forks of the same note, Tacoma Narrows Bridge, a boy bounc ing a ball , a child be ing pushed on a swing, a s inger shattering a g lass . • Standi ng waves with increasing numbers of nodes create harmonics in a vibrating object.

Pra ctice Problems:

I. Draw a transverse wave and labe l: Wavelength, ampli tude, crest, trough.

2 . Draw a spring pulse mov ing toward a fi xed end then draw the re fl ected pulse as it travels back. (i nclude d irection arrows) .

Pulse Toward F ixed end Reflected pulse

4. The transverse wave below represents the air pressure of a (long itudina l) sound wave traveling in the air. . Use it to answer the following questions: ( in all cases, assume the same medium)

ve that has greater energy:

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( k-, t- Vt'" slNW") / lower frequency:

~ ~ c. Dra2awave that had the same pitch but was softer:

d. Draw a wave that would have a higher pitch:

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Ie e. Which of the waves that you drew has the longest wavelength (a, b, c, d)? ___ _

f. Whi ch of the waves you drew wou ld trave l the s lowest? All S<iMR.-.

g. Wh ich of the waves you drew has the highest frequency? J 5. Describe two situations where resonance can be observed.

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6. Explain with a sketch why an ambulance siren sounds higher pitched when approachi ng you and lower pitched when moving away from you.

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8. Describe th ree different ways that pitch can be maniR,;ilated in a guitar to make music.

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9. Guitars and pianos are both stringed instruments. Why do they sound so di fferent?

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10. Draw the fundamental and second and third harmonics of a standing wave moving between the endpoi nts shown below. Wh ich note wi ll have the lowest pitch? Wh ich 2 notes will be octaves? Label the nodes, anti-nodes, amplitude and wavelength for the third harmonic.

Fundamental: Second Harmonic:

IE ___ ~ IE_ =><_ J1 Th ird Harmonic: ~ :>1

II. Why do longer objects make lower-pitched notes than short objects?

~.v~,w,.+~ ( ~ v~<-7 hp<s (07-r), 12. The speed of sound in fresh water at 20°C is 1482 m/sec, whil e it is 1522 m/sec in seawater at 20°C. Why

do you think it is faste r in seawater?

lu)~ tbt'J:~ 13. Two bottlenose dolphins are carry ing on a long distance conversat ion. If they are 200 km apart, and the

speed of sound in seawater is 1.522 km/sec, how long will it take one dolphin to hear the other?

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14. The bott le nose dolphins are communicating at a frequency of 100,000 Hz. What is the wavelength of these waves in seawater (v = 1522 m/sec)?

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IS. If a girl is bouncing a ball with a frequency of2 bounces/seco nd , what isthe period of bouncing?

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Name: ____________________________ ___ Period: Waves Extra Practice

l -.-babel-the ,wave,below ·with-the,followingo,Wavclength',-·Amp litudc,-,C"ost'i-T'Dugh

2cWhatkindofwave' isdrawninquestionl? ________ ... _ .... _ .... _,._',._" _-'_._ .... _--_"_ .. ,_-_'-___ --_- _-___ '-_-_-~~_-_-_-_--__ - '

3. Label the picture below with: rarefact ion, compression, wavelength

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4. In the standing wave pictured be low, label: Antinode, Node

5. Describe what creates a standing wave: Wi{ lit "7 V/ / SA o/IA-'-

),,'~-HI~C, i\J\~~ue.. ~ 6. Which of t hese is not related to frequency?

A. amplitude B. wavelength

-IL- 7. Which of these affects wave speed? A. the tension of a spring. C. The type of medium it travels in B. the density of the medium. the-shap~f-t-he-wave~ D. All the above

c 8. Sound trave ls fastest in A. gases. B. liquids. C. sol ids.

~ 9. To increase the number of anti-nodes in a standing wave, A. the frequency must be increased. C. the amplitude must be increased. B. the wavelength must be increased. D. all of the above.

L 10. The amplitude of a longitudina l wave is measured by A .. the amount of medium displaced by the waves. C. the distance between compressions. B. the height of a compression wave. D. the amount of compression in the waves

L 11. If the frequency of a wave was doubled from its original va lue (in the same medium), the A. wavelength would be doubled. C. amplitude would decrease. B. wavelength would be halved D. amplitude would increase.

12. Use the pictures below to draw what would happen at the point of interference.

A.

B.

13. Which wavers) above (A, B) will destructively interfere? B -11-14. After the waves in the pictures interact, they will

Draw the interference be low

Draw the interference below

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A. bounce off each other. C. continue to affect each other. B. pass through each other. D. none of the above.

l ls. What do waves transfer? A. material B. energy C. A and B D. waves do not transfer anything.

Light, etcetera

I) What is waving in a light wave?

E(erAvtc d- )1//t71)~ f,r)js 2) Is li g t ransver e r longitudinal?

3) Which has a longer wave length (in the same med ium) red li gl or x-rays?

4) Wh ich has a lower frequency (in the same med ium): ultraviolet li ght 0 microwaves.

5) What is fi ssion? 1\ vc(ecw s~I(e.--

6) Where does fusion occur?

S{.:vS 7) Why won' t the sun become a black hole?

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