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Warm-Up: March 27th

Warm-Up: March 27th. What are the two types of mechanical waves? Sound is what kind of wave? What is the topmost part of a transverse wave called? What makes up the wavelength of a longitudinal wave (what two parts) ?

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Warm-Up: March 27th

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  1. Warm-Up: March 27th • What are the two types of mechanical waves? • Sound is what kind of wave? • What is the topmost part of a transverse wave called? • What makes up the wavelength of a longitudinal wave (what two parts)? • If you can see the light coming from another room (not directly), the lightwaves are bending. What do we call that?

  2. Sound Waves • Longitudinal – • Disturbance of medium is parallel to wave movement • MUST have a medium to travel in

  3. V  f Wave Speed • Velocity of a wave is calculated by multiplying wavelength by frequency • Vw=  x f *As f increases,  decreases!

  4. Example Problem 1: • A wave is generated in a wave pool at an amusement park. The wavelength is 3.2 m and the frequency is 0.60 Hz. What is the velocity of the wave? • V = x f 1.92 m/s

  5. Example Problem 2: • Earthquakes can produce three types of waves. One of these is a transverse wave called an “s” wave. A typical s wave travels at 5000 m/s. Its wavelength is 417 m. What is its frequency? • F = 12 Hz

  6. Example Problem 3: • A sound wave has a frequency of 500.0 Hz and a wavelength of 3.0 m. What is the speed of the wave? • V = x f

  7. Example Problem 4 • The lowest-pitched sounds humans can hear have a frequency of 20.0 Hz. What is the wavelength of these sound waves if their wave speed is 340.0 m/s? • V = x f

  8. Warmup March 28th Happy Spring Break!! • What kind of waves are sound waves? • Longitudinal • Electrical • Transverse • Both A and B

  9. 2. As frequency of a wave Increases, the length of a wave ___________(if velocity is same) • Increases • Stays the Same • Decreases

  10. 3. Sound travels fastest through • Solid • Liquid • Gas

  11. 4. Frequency of a wave determines a sound’s • Amplitude • Pitch • Intensity

  12. 5. What is the Frequency of a sound wave traveling 330m/s (in the air) with a wavelength of .55 meters? • 1550 Hz • 800 Hz • 775 Hz • 600 Hz

  13. ANSWERS TO WARMUP 1.A 2.C 3.A 4.B 5.D

  14. Frequency and Pitch • Pitch: The highness or lowness of sound • Depends on the frequency • High frequency = high pitch • Low frequency = low pitch • 20,000 Hz: ultrasonic waves • 20 Hz and below: infrasonic waves

  15. Intensity and Loudness • Loudness: Human perception of sound intensity. • Depends on the amplitude • Decibel Scale (dB) - Measures intensity of sound

  16. Waves go through mediums, and different mediums are transparent to different types of wave energy. But also, a wave’s energy can be partly or completely absorbed by the different medium When Waves Hit Things

  17. Sound – as Waves • Amplitude = volume • Frequency = pitch. High frequency, high pitch. Low frequency, low pitch. • Must have a medium – no medium, no sound. • Sound waves – What type of medium do they travel fastest through (solid, liquid, gas)?

  18. Measuring Sound • Decibel – a measure of the Sound Pressure Level. The higher the decibel, the more intense the sound.

  19. It happened to my uncle…he was one of the first people I ever knew to own a “SONY WALKMAN”He listened at very high volumes pretty much all day…now he is pretty much deaf……and it’s very much annoying for us and him!

  20. DID YOU HEAR WHAT I SAID???DON’T LET THIS HAPPEN TO YOU!!!!!!!!

  21. August 27, 1883 • Krakatoa • 180 dB • Loudest sound ever heard. • The sound itself caused tsunamis

  22. The Doppler EffectThe What?????Where have you heard the term “doppler” before? • http://www.youtube.com/watch?v=h4OnBYrbCjY&authuser=0 • http://www.youtube.com/watch?v=Djz_rtnXSfY&authuser=0

  23. The Doppler Effect • A change in the observed frequency of a wave when the source and observer (you) are in motion relative to each other. • The frequency appears to increase as the source get closer, and appears to decrease as it moves away.

  24. Cool sound stuff… • Supersonic (faster than the speed of sound) • Subsonic (slower than the speed of sound) • Sonic boom (what happens when you pass the speed of sound) • Infrasound (below 20 Hz)

  25. Sound Waves Carry Energy!! • https://www.youtube.com/watch?v=BE827gwnnk4

  26. Calculate the Wavelength of 3 different tuning forks Vw=  x f Speed of sound in air is 330m/s The frequency of each fork is printed on the stem Calculate the wavelength of three different tuning forks. 256, 312, 680

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