# Chapter 21.

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Chapter 21

Two pulses on a string approach each other at speeds of 1 m/s
Two pulses on a string approach each other at speeds of 1 m/s. What is the shape of the string at t = 6 s? IG20.1 (1) (2) (3) (4)

Two pulses on a string approach each other at speeds of 1 m/s
Two pulses on a string approach each other at speeds of 1 m/s. What is the shape of the string at t = 6 s? IG20.1 (1) (2) (3) (4)

A standing wave on a string vibrates as shown at the top
A standing wave on a string vibrates as shown at the top. Suppose the tension is quadrupled while the frequency and the length of the string are held constant. Which standing wave pattern is produced? STT21.2 (1) (2) (3) (4) (5)

A standing wave on a string vibrates as shown at the top
A standing wave on a string vibrates as shown at the top. Suppose the tension is quadrupled while the frequency and the length of the string are held constant. Which standing wave pattern is produced? STT21.2 (1) (2) (3) (4) (5)

An open-open tube of air supports standing waves at frequencies of 300 Hz and 400 Hz, and at no frequencies between these two. The second harmonic of this tube has frequency Hz. Hz. Hz. Hz. Hz. STT21.3

An open-open tube of air supports standing waves at frequencies of 300 Hz and 400 Hz, and at no frequencies between these two. The second harmonic of this tube has frequency Hz. Hz. Hz. Hz. Hz. STT21.3

1. Move speaker 1 backward (to the left) 0.5 m.
Two loudspeakers emit waves with l = 2.0 m. Speaker 2 is 1.0 m in front of speaker 1. What, if anything, must be done to cause constructive interference between the two waves? 1. Move speaker 1 backward (to the left) 0.5 m. 2. Move speaker 1 backward (to the left) 1.0 m. 3. Move speaker 1 forward (to the right) 1.0 m. 4. Move speaker 1 forward (to the right) 0.5 m. 5. Nothing. The situation shown already causes constructive interference. STT21.4

1. Move speaker 1 backward (to the left) 0.5 m.
Two loudspeakers emit waves with l = 2.0 m. Speaker 2 is 1.0 m in front of speaker 1. What, if anything, must be done to cause constructive interference between the two waves? 1. Move speaker 1 backward (to the left) 0.5 m. 2. Move speaker 1 backward (to the left) 1.0 m. 3. Move speaker 1 forward (to the right) 1.0 m. 4. Move speaker 1 forward (to the right) 0.5 m. 5. Nothing. The situation shown already causes constructive interference. STT21.4

The interference at point C in the figure at the right is
1. maximum constructive. 2. destructive, but not perfect. 3. constructive, but less than maximum. 4. there is no interference at point C. 5. perfect destructive. STT21.5

The interference at point C in the figure at the right is
1. maximum constructive. 2. destructive, but not perfect. 3. constructive, but less than maximum. 4. there is no interference at point C. 5. perfect destructive. STT21.5

These two loudspeakers are in phase
These two loudspeakers are in phase. They emit equal-amplitude sound waves with a wavelength of 1.0 m. At the point indicated, is the interference maximum constructive, perfect destructive or something in between? STT21.6 1. maximum constructive 2. perfect destructive 3. something in between

These two loudspeakers are in phase
These two loudspeakers are in phase. They emit equal-amplitude sound waves with a wavelength of 1.0 m. At the point indicated, is the interference maximum constructive, perfect destructive or something in between? STT21.6 1. maximum constructive 2. perfect destructive 3. something in between

You hear three beats per second when two sound tones are generated
You hear three beats per second when two sound tones are generated. The frequency of one tone is known to be 610 Hz. The frequency of the other is Hz. Hz. Hz. Hz. 5. Either 2 or 3. STT21.7

You hear three beats per second when two sound tones are generated
You hear three beats per second when two sound tones are generated. The frequency of one tone is known to be 610 Hz. The frequency of the other is Hz. Hz. Hz. Hz. 5. Either 2 or 3. STT21.7

1. Shape unchanged, amplitude unchanged
When a wave pulse on a string reflects from a boundary, how is the reflected pulse related to the incident pulse? 1. Shape unchanged, amplitude unchanged 2. Shape inverted, amplitude unchanged 3. Shape unchanged, amplitude reduced 4. Shape inverted, amplitude reduced 5. Amplitude unchanged, speed reduced IG21.1

1. Shape unchanged, amplitude unchanged
When a wave pulse on a string reflects from a boundary, how is the reflected pulse related to the incident pulse? 1. Shape unchanged, amplitude unchanged 2. Shape inverted, amplitude unchanged 3. Shape unchanged, amplitude reduced 4. Shape inverted, amplitude reduced 5. Amplitude unchanged, speed reduced IG21.1

There are some points on a standing wave that never move
There are some points on a standing wave that never move. What are these points called? 1. Harmonics 2. Normal Modes 3. Nodes 4. Anti-nodes 5. Interference IG21.2

There are some points on a standing wave that never move
There are some points on a standing wave that never move. What are these points called? 1. Harmonics 2. Normal Modes 3. Nodes 4. Anti-nodes 5. Interference IG21.2

Two sound waves of nearly equal frequencies are played simultaneously
Two sound waves of nearly equal frequencies are played simultaneously. What is the name of the acoustic phenomena you hear if you listen to these two waves? 1. Beats 2. Diffraction 3. Harmonics 4. Chords 5. Interference IG21.3

Two sound waves of nearly equal frequencies are played simultaneously
Two sound waves of nearly equal frequencies are played simultaneously. What is the name of the acoustic phenomena you hear if you listen to these two waves? 1. Beats 2. Diffraction 3. Harmonics 4. Chords 5. Interference IG21.3

The various possible standing waves on a string are called the
1. antinodes. 2. resonant nodes. 3. normal modes. 4. incident waves. IG21.4

The various possible standing waves on a string are called the
1. antinodes. 2. resonant nodes. 3. normal modes. 4. incident waves. IG21.4

The frequency of the third harmonic of a string is
1. one-third the frequency of the fundamental. 2. equal to the frequency of the fundamental. 3. three times the frequency of the fundamental. 4. nine times the frequency of the fundamental. IG21.5

The frequency of the third harmonic of a string is
1. one-third the frequency of the fundamental. 2. equal to the frequency of the fundamental. 3. three times the frequency of the fundamental. 4. nine times the frequency of the fundamental. IG21.5