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Vibrations and Waves Wave: A Disturbance That Travels Or…
A Wiggle in Space
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Wavelength (λ) = Distance from one crest to the next crest.
Measured in meters. Frequency (f) = Number of vibrations every second. Measured in Hertz (cycles/second). Amplitude = Distance from the midline to the crest. Measured in meters. Period = Time needed to make one vibration.
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Slinky Slinky: A spring that is very flexible, lots of mass
Who walks the stairs without a care It shoots so high in the sky. Bounce up and down just like a clown. Everyone knows its Slinky. The best present yet to give or get. The kids will all want to try. The hit of the day when you are ready to play. Everyone knows it's Slinky. It’s Slinky, It’s Slinky for fun the best of the toys. It’s Slinky, It’s Slinky the favorite of girls and boys. Slinky: A spring that is very flexible, lots of mass
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Vibration is perpendicular to the
Transverse Waves Vibration is perpendicular to the direction of the wave.
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Vibration is parallel to the
Longitudinal Waves Vibration is parallel to the direction of the wave.
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There are no sounds in space!
Sound: Vibration of a material substance that has a frequency the human ear can pick up. Sounds are longitudinal waves. There are no sounds in space!
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Compression: The air (or other material) is compressed. High pressure.
Rarefaction: The air (or other material) is spread out. Low pressure.
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Not Just Air! Many media can produce sound waves. Must possess “elasticity.” Elasticity: The ability to distort and then “rebound” back to normal. Water and Steel are examples of elastic substances that can transmit sound.
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Waves Generated by Earthquakes
P-waves: Longitudinal. S-waves: Transverse.
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The reflection of sound is called an echo.
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Anechoic Chamber: A room designed to eliminate reflections.
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Refraction of Sound Waves
Sound waves can bend (refract) The warmer the air, the faster sound travels. At room temperature, speed travels at about 344 m/s.
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Forced Vibrations One vibrating object forces another to vibrate.
Acoustic string Instruments.
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A forced vibration that matches an objects
Resonance A forced vibration that matches an objects natural frequency. Tacoma Narrows Bridge
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Interference Multiple waves add and subtract from each other.
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Examples of Interference
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Standing Waves Nodes and Antinodes
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½ λ 1 λ 1½ λ
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Doppler Effect If the source of a wave is moving towards or away from you, the frequency changes.
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Bow Waves and Shock Waves
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Creation of Bow Waves
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MUSIC Noise is random, music is organized
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Instruments differ in the type and mixture of
harmonics.
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Energy in Sound Waves Energy of 10,000,000 people talking at once
would barely power a common flashlight. Sound energy is stored in the compression (potential energy) and released in the rarefaction (kinetic energy).
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