Question 1

A stationary siren emits sound of frequency 1000 Hz and wavelength 0.343 m.An observer who is moving toward the siren will measure a frequency f and wavelength λ for this sound such that

Accepted Answer

A) f > 1000 Hz and λ > 0.343 m. B) f > 1000 Hz and λ = 0.343 m. C) f > 1000 Hz and λ < 0.343 m. D) f = 1000 Hz and λ < 0.343 m.

Question 2

A plane flies toward a stationary siren at 1/4 the speed of sound.Then the plane stands still on the ground and the siren is driven toward it at 1/4 the speed of sound.In both cases,a person sitting in the plane will hear the same frequency of sound from the siren.

Accepted Answer

A) True 
 B)False

Question 3

Two people are talking at a distance of 3.0 m from where you are and you measure the sound intensity as 1.1 × 10-7 W/m2.Another student is 4.0 m away from the talkers.What sound intensity does the other student measure? Assume that the sound spreads out uniformly and undergoes no significant reflections or absorption.

Accepted Answer

A) 6.2 × 10-8 W/m2 
B) 1.5 × 10-7 W/m2 
C) 8.3 × 10-8 W/m2 
D) 7.8 × 10-7 W/m2 
E) 2.5 × 10-8 W/m2

Question 4

A factory siren indicating the end of a shift has a frequency of 90.0 Hz.The speed of sound is 343 m/s.
(a)What frequency is perceived by the occupant of a car traveling towards the factory at
25.0 m/s?
(b)What frequency is perceived by the occupant of a car traveling away from the factory at
30.0 m/s?

Accepted Answer

The answer of A factory siren indicating the end of...

Question 5

Four traveling waves are described by the following equations,where all quantities are measured in SI units and y represents the displacement. I: y = 0.12 cos(3x + 2t)
II: y = 0.15 sin(6x - 3t)
III: y = 0.23 cos(3x + 6t)
IV: y = -0.29 sin(1.5x - t)
Which of these waves have the same speed?

Accepted Answer

A) I and III 
B) I and IV 
C) II and III 
D) I and II 
E) III and IV

Question 6

Waves travel along a 100-m length of string which has a mass of 55 g and is held taut with a tension of 75 N.What is the speed of the waves?

Accepted Answer

A) 3700 m/s 
B) 370 m/s 
C) 37 m/s 
D) 0.37 m/s 
E) 3.7 m/s

Question 7

The howler monkey is the loudest land animal and,under some circumstances,can be heard up to a distance of 8.9 km.Assume the acoustic output of a howler to be uniform in all directions and that the threshold of hearing is 1.0 × 10-12 W/m2.A juvenile howler monkey has an acoustic output of  What is the ratio of the acoustic intensity produced by the juvenile howler to the reference intensity I0,at a distance of 210 m?

Accepted Answer

A) 110 
B) 230 
C) 76 
D) 170 
E) 300

Question 8

The figure shows the displacement y of a traveling wave at a given position as a function of time and the displacement of the same wave at a given time as a function of position.How fast is the wave traveling?

Accepted Answer

A) 3.0 m/s 
B) 0.75 m/s 
C) 0.66 m/s 
D) 1.5 m/s 
E) 2.0 m/s

Question 9

A transverse wave traveling along a string transports energy at a rate r.If we want to double this rate,we could

Accepted Answer

A) increase the amplitude of the wave by a factor of 8. 
B) increase the amplitude of the wave by a factor of 4. 
C) increase the amplitude of the wave by a factor of 2. 
D) increase the amplitude by a factor of  . 
E) increase the amplitude by a factor of  .

Question 10

At a distance of 2.00 m from a point source of sound,the intensity level is 80.0 dB.What will be the intensity level at a distance of 4.00 m from this source? The lowest detectable intensity is 1.0 × 10-12 W/m2.

Accepted Answer

A) 77.0 dB 
B) 74.0 dB 
C) 60.0 dB 
D) 40.0 dB 
E) 20.0 dB

Question 11

What characteristic of sound determines the "pitch" of a musical note?

Accepted Answer

A) amplitude 
B) wavelength 
C) frequency 
D) phase 
E) intensity

Exam 16: Traveling Waves