Ch.
21
Ch.
21 Section reviews
Page 605:
1. A sound wave is carried through a medium by longitudinal waves.
2. B
5. All sounds are carried by longitudinal waves, the particles don’t move forward with the wave.
6. No, there is no medium between the moon and Earth to carry sound.
8. a longitudinal wave
9. dense areas are compressions and sparse areas are rarefactions
10. The back and forth motion of a vibrating object forms compressions and rarefactions in the air around it.
Page 611:
1. How low or how high a sound seems depends on the frequency of the sound waves
2. Loudness is expressed scientifically in units of decibels
3. C
4. Sound travels fastest in higher temperature media
5. Pitch is determined by the frequency of sound waves
6. An oscilloscope changes sound waves into electronic signals which are seen on a screen as transverse waves
7. 343m/s x 2 s = 686m
8. 1,500 m/s x 4 s = 6,000m
9. Yes, sound waves in front of the source will become closer together as the source moves forward. Also, the listener will “meet” the sound waves more rapidly by moving toward the source. Movements of the source and the listener will make the pitch of the sound higher.
10. The amplitude of the sound will be higher when the drum is struck harder. The frequency will not change.
Page 617:
1. Some animals use echolocation to “see” in the dark by listening for the echoes of the sounds they make off reflected objects.
2. standing waves
3. resonance
4. A
5. a room with smooth walls
6. Use echolocation to find insects by emitting sounds then listening to the echoes to tell how far away and how fast the insect is moving.
7. Constructive interference: sonic boom, destructive interference: “dead spot” in a concert hall
8. 343m/s x 0.05 s = 17 m 17m ?2 =8.5m
9. Resonance is occurring, the lamp has a resonant frequency equal to one of the notes being played.
10. Both make use of sound reflection to locate objects. Ultrasonography involves much higher frequency sound waves than used in sonar and allows imaging of objects instead of just locating them.
Page 621:
1. Each instrument has a different sound quality based on how it produces sound. Static on the TV or radio is noise.
2. D
3. A musical instrument’s particular shape and way of producing sound gives it its unique sound quality.
4. String and wind both make standing waves, string instruments along the string, wind inside the air column.
6. Music because of a repeating pattern.
Page 626 - 627
1. A
2. B
3. D
4. B
5. C
6. A
7. C
8. D
9. C
4. B
5. C
6. A
7. C
8. D
9. C
