PS 1-3-08 Waves and Sound. New Website address .
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Transcript of PS 1-3-08 Waves and Sound. New Website address .
![Page 1: PS 1-3-08 Waves and Sound. New Website address .](https://reader036.fdocuments.us/reader036/viewer/2022062519/5697c0041a28abf838cc4550/html5/thumbnails/1.jpg)
PS 1-3-08
Waves and Sound
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New Website address
• www.Elyceum.wikispaces.com
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Time until exams
• About a week of class time towards new material
• Waves, sound, light, and maybe color
• Some graded exercise on next Wednesday
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Mid-year exam
• Review next Thursday and Friday
• Find your old tests
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Waves
• Interference
• Constructive interference
• Destructive interference
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• Relationship between type of interference and amplitude size
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Interference and bubbles
• Constructive and destructive interference creates rainbow effect on bubbles
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Interference and sound
• Keeping a piano in tune
• Dead Spots in a room
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Standing waves
• Occurs where at least one end of wave is fixed
• Relationship between incoming wave and reflected wave
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Standing waves in guitar
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Nodes
• Place along medium of complete destructive interference
• Crest of incoming cancels trough of reflected (or vice versa)
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Antinodes
• Place of maximum vibration
• Constructive interference
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Tacoma Narrows Bridge
• Wind created a standing wave with in structure of bridge
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Homework
• Page 478
• Problems 1-6
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Sound
• Type of wave
• Speed of Sound
• 331m/s @ 0°C to 386 @ 25C
• 1490-1530 C in water
• 3800-5000 C
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Loudness
• Depends on the energy in the sound wave
• Intensity = rate of energy transmission through a given area of the medium
• Greater Intensity Louder sound
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Measure of Loudness
• Relative intensity
• Compares the intensity of the sound with the intensity of the quietest sound that a person can hear
• Measured in decibels
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Decibel scale
• 0 dB threshold of hearing
• 30 dB whispering
• 50dB normal conversation
• 70dB vacuum cleaner
• 90 dB lawnmower
• 120 dB threshold of pain
• 150 dB nearby jet airplane
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Pitch
• Not related to loudness
• Related to the frequency of wave
• Humans range of hearing range from– 20 HZ to 20,000 HZ
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Sound beyond human range
• Lower than 20 Hz Infrasound
• Higher than 20,000 Hz ultrasound
• Dogs can hear to 46,000 Hz
• Dolphins can hear to 150,000 Hz
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Echos
• What is needed to create an echo?
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Places you here an echo
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Ultrasound
• Ultrasonic waves are generated and moves away from the source
• They hit an object and reflect back to the source
• The time it takes for the wave to return is recorded and used to find the distance object is from source D = v t
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Example of ultrasound use
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Why use ultrasonic waves?
• Focused into more narrow beams
• Directed more easily
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SONAR
• Sound, Navigation, and RAnging
• Uses acoustic signals and echo returns to locate objects