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G12 WORKSHEET 3 SOUND WAVES

Chapter (15) Section (1) Subject Sound

Name Date

Grade 12 Cluster

I-Choose the best answer:

1. When sound travels through air, the air particles ______

A. vibrate along the direction of wave propagation

B. vibrate but not in any fixed direction

C. vibrate perpendicular to the direction of wave propagation

D. do not vibrate

E. B & C

2 . The amplitude of a wave is ______

A. the distance the wave moves in one second

B. the distance the wave moves in one time period of the wave

C. the maximum distance moved by the medium particles on either side of the mean position

D. the distance equal to one wave length

E. the minimum distance moved by the medium particles on either side of the mean position

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4. A sound source sends waves of 800 Hz. It produces waves of wavelength 2.5 m. The velocity of

sound waves is_______

A. 200 m/s

B. 2000 m/s

C. 20000 m/s

D. 300 m/s

E. 3000 m/s

5.Sound level is a measure of _____.

A. amplitude

B. Frequency

C. Wavelength

D. Pitch

E. Speed

6.Due to the Doppler effect, the _____ of a sound increases as the source approaches you.

A. amplitude

B. frequency

C. wavelength

D. pitch

E. speed

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II- Solve the following problems

7. What is the wavelength of a 6.00102-Hz sound wave in air at 20C?

8. A 171.5-Hz sound wave has a wavelength of 2 m in an unknown medium. Identify the medium.

9. The frequency of a certain police cars siren is 1550 Hz when at rest. What frequency do you

detect if you move with a speed of 30.0 m/s?

a) Toward the car,

fd=fs(1-vd/v)

fd=1550(1-30/343)fd=-131.0hz

B) Away from the car?

fd=fs(1-vd/v)

fd=1550(1--30/343)

fd=140.0hz

10. A bird is flying directly toward a stationary bird-watcher and emits a frequency of 1250 Hz.

The bird-watcher, however, hears a frequency of 1290 Hz. What is the speed of the bird?

fd=fs(1-vd/v)

1290=1250(1-vd/343)

1250/1290=1250(1-vd/343)/ 1250

343x1.032=1-vd/343x343

353.976=1-vd

vd=-352.976m/s

11. You hear the siren of a fire engine as you stand on the side of the road. As it approaches, the

siren which broadcasts at a frequency of 645 Hz is heard by you as being 660 Hz. How fast is the

fire engine traveling? The speed of sound in air is 343 m/s.

645/660=645(1/1-vs/343)/645

343x1x1.023=1/1-vs/343x343x1

1x351=1/-vsx1

343=6.00102xL

L=5716.66m

171.5x2=343m/s>air at 20

331+(0.6x20)=343

lamda=v/f

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351=-vs vs=351m/s

III Answer the following questions:

List two sound characteristics that are affected by the medium through which the sound passes

and two characteristics that are not affected.

The speed of sound and the wavelength of the sound are affected by the medium. Theperiod of the wave and the frequencyof the wave are unaffected.