- 16

- 0

1. Homework Statement

Two identical loudspeakers separated by distance d emit 170 Hz sound waves along the x-axis. As you walk along the axis, away from the speakers, you don't hear anything even though both speakers are on. What are three possible values for d? Assume a sound speed of 340 m/s.

2. Homework Equations

phase difference = 2*Pi*(change in r/wavelength)+initial phase difference=2(m+1/2)Pi

interference is destructive if the path-length difference r=(m+1/2)wavelength

3. The Attempt at a Solution

find the wavelength

f=v/2L = v/wavelength

wavelength=v/f =340/170 =2

d=(m+1/2)wavelength

for m=0: d=1m

m=1: d=2m

m=2 d=3m

did I do this correctly?

1. Homework Statement

A steel wire is used to stretch a spring. An oscillating magnetic field drives the steel wire back and forth. A standing wave with three antinodes is created when the spring is stretched 8.0cm. What stretch of the spring produces a standing wave with two antinodes

2. Homework Equations

unsure

3. The Attempt at a Solution

the wave is in the third harmonic. The wavelength can be found using

wavelength=4L/m =4(.08)/3 = 8/75

I'm not sure how to get to the book's answer of 18 cm.

1. Homework Statement

Two loudspeakers 5.0m apart are playing the same frequency. If you stand 12.0 m in from of the plane of the speakers, centered between them, you hear a sound of maximum intensity. As you walk parallel to the plane of the speakers, staying 12.0m in front of them, you first hear a minimum of sound intensity when you are directly in from of one of the speakers.

a. what is the frequency of the sound? Assume a sound speed of 340 m/s

b. If you stay 12.0m in front of one of the speakers, for what other frequencies between 100 Hz and 1000 Hz is there a minimum sound intensity at this point?

2. Homework Equations

unsure for part b

3. The Attempt at a Solution

I've solved part a, f=170 Hz.

I don't even know how to start part b.