Chapter 16

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Chapter 17

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Reading: sections 16.1 – 16.5, 16.7, 16.9; 17.1 – 17.3, 17.5 – 17.8

Outline:

mechanical, electromagnetic, and matter waveswave speed

introduction to waves

transverse and longitudinal wavesamplitude and phasewavelength and frequencywave speedsinusoidal waves

traveling waves

waves speed on a stretched string

waves in two- and three-dimensions

the principle of superposition

Standing waves on a string standing waves

interference in one-dimensionconstructive and destructive interferencephase differenceinterference in two- and three-dimensionsbeats

interference

Conceptual Question 16.A In the figure below, five points are indicated on a snapshot of a sinusoidal wave. What is the phase difference between point 1 and (a) point 2, (b) point 3, (c) point 4, and (d) point 5? Answer in radians and in terms of the wavelength of the wave. The snapshot shows a point of zero displacement at x = 0. In terms of the period T of the wave, when will (e) a peak and (f) the next point of zero displacement reach x = 0?

Problem 17.22Two loud speakers emit sound waves along the x-axis. The sound has maximum intensity when the speakers are 20 cm apart. The sound intensity decreases as the distance between the speakers is increased, reaching zero at a separation of 30 cm. (a) What is the wavelength of the sound? (b) If the distance between the speakers continues to increase, at what separation will the sound intensity again be a maximum?

Problem 17.62Two loudspeakers emit sound waves along the x-axis. A listener in front of both speakers hears a maximum sound intensity when speaker 2 is at the origin

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Two loudspeakers emit sound waves along the x-axis. A listener in front of both speakers hears a maximum sound intensity when speaker 2 is at the origin and speaker 1 is at x = 0.50 m. If speaker 1 is slowly moved forward, the sound intensity decreases and then increases, reaching a maximum when speaker 1 is at x = 0.90 m. What is the frequency of the sound? Assume vsound = 340 m/s.

Problem 7 A pair of in-phase stereo speakers are placed next to each other, 0.60 m apart. You stand directly in front of one of the speakers, 1.0 m from the speaker. What is the lowest frequency that will produce constructive interference at your location? Assume vsound = 340 m/s.

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Q16-3) A source of frequency f sends waves of wavelength ̧traveling with speed v in some medium. If the frequency is changed from f to 2f, then the new wavelength and new speed are (respectively):

A) 2 v

B) /2 v

C) 2v

D) v/2

E) /2 2v

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B) /2 v

C) 2v

D) v/2

E) /2 2v

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Interference Applets:17 -

Interferen...17 -

Interferen...

https://ngsir.netfirms.com/j/Eng/waves/waves_js.htmTypes of Waves Applet:

http://physics.bu.edu/~duffy/HTML5/interference.htmlConstructive and Destructive Interference Applet:

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Thursday, May 14, 2020 11:54 AM

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