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Chapter 17

Chapter 17. WAVES. What is a Wave?. Waves -rhythmic disturbances that carry energy through matter or space Medium -material through which a wave can travel and transfer energy *solid, liquid, gas, or combination. Three main types.

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Chapter 17

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  1. Chapter 17 WAVES

  2. What is a Wave? • Waves-rhythmic disturbances that carry energy through matter or space • Medium-material through which a wave can travel and transfer energy • *solid, liquid, gas, or combination

  3. Three main types • Transverse Wave-medium move at right angle to direction of wave • Longitudinal Waves-matter vibrates in the same direction as the wave travels, parallel • Surface Wave-travels along a surface separating two media, most common are ocean waves

  4. Transverse Wave Wavelength Crest Amplitude _ _ _ _ _ _ _ _ _ _ _ _ _ _ _rest point (equilibrium) _ _ Trough

  5. Transverse Wave • Crest-highest point of the wave above the rest point • Trough-lowest point below the rest point • Wavelength-distance between a point on one wave and the same point on the next cycle of the wave

  6. Transverse Wave • Amplitude-max displacement of the medium from its rest point, corresponds to the amt. of energy a wave carries (more energy = greater amplitude)

  7. Transverse Wave • Frequency-# of wavelengths that pass a fixed point each second, measured in Hertz (Hz) (Increasing Frequency = wavelength decreases) • Period-time it takes for one wavelength to pass a point (Increasing Frequency = period decreases)

  8. Longitudinal Waves Longitudinal Waves-matter vibrates in the same direction as the wave travels, parallel

  9. Longitudinal Waves aka compressional waves • compression-area where particles in a medium are spaced close together • rarefaction-area where particles in a medium are spread out

  10. Surface Wave Surface Wave-travels along a surface separating two media, most common are ocean waves

  11. Wave velocity Wave speed frequency wavelength Velocity of wave = wavelength x frequency V w =  (lambda) x f [m/s] = [m] x [Hz]

  12. Wave Speed • One end of a rope is vibrated to produce a wave with a wavelength of 0.25meters. The frequency of a wave is 3 hertz. What is the speed of the wave?

  13. Wave Speed • Wavelength = 0.25m • Frequency = 3Hz • Speed =?

  14. Transverse Wave & Friends • Draw a transverse wave (from your notes) • Label the following parts on the wave and then define them below the wave: • Crest - Amplitude - Trough • Wavelength - Rest point (equilibrium) • Give an example of a transverse wave • At the bottom, list the other two wave types, define them, and draw small pics for them!

  15. Behavior of waves • Reflection • wave bounces off a surface that it cannot pass through • does not change speed or frequency, but wave can be flipped upside down

  16. Reflection

  17. Behavior of waves • Refraction • bending of a wave as it enters a new medium at an angle • one side of the wave moves more slowly than the other side

  18. Refraction

  19. Behavior of waves • Diffraction • bending of wave as it moves around an obstacle or passes through a narrow opening • diffracts more of its wavelength if large compared to the size of an opening or obstacle

  20. Diffraction

  21. Behavior of waves • Interference • occurs when two or more waves overlap and combine together • Two types • constructive-the waves add together • destructive-the waves subtract from each other as they overlap

  22. Constructive

  23. Destructive

  24. Node versus Antinode

  25. Behavior of waves • Polarization • Light with waves that vibrate in one plane is polarized light • Horizontal filter blocks waves vibrating on a vertical plane • Vertical filter blocks waves vibrating on a horizontal plane

  26. Polarization

  27. IAN page 40: How Waves Behave • Determine which picture represents each of the following wave behaviors and label them: • Reflection, refraction, constructive interference, destructive interference, diffraction, polarization • Cut them out and glue them on to page 40 • Under each picture, write the definition for the behavior from the textbook (pg. 508-511) • Don’t worry about writing the def. for polarization! • Make sure under the constructive/destructive interference pics you write their specific definitions!

  28. Sound Speed of sound depends on: • type of medium-solid is the best conductor *no sound on moon or in space • temperature of medium-faster at higher temps

  29. Sound • Intensity – rate at which a wave’s energy flows through a given area • Loudness – human perception, measured in decibels (dB)

  30. Sound Pitch – highness or lowness of a sound • high frequency = high pitch • low frequency = low pitch • humans hear between 20 & 20,000 Hz • Ultrasonic is above 20,000 Hz • Infrasonic (subsonic) is below (thunder)

  31. Sound • Resonance– if the sound that reaches an object is at the same frequency of the object, the object will begin to vibrate at that frequency • Noise pollution– includes sounds that are loud, annoying or harmful to the ear

  32. Why do concert places usually have carpet on walls and floors?

  33. Doppler effect • A change in sound frequency caused by motion of the sound source, motion of the listener, or both • Higher pitch, higher frequency as object approaches • Lower pitch, lower frequency as sound source moves away

  34. Laurel or Yanny??? • In your groups… • Research the debate on Laurel or Yanny • Decide what you hear • Listen to it on multiple phones • Listen to it through ear buds • Listen to it through multiple sources • Write an explanation! • Must be at least one paragraph consisting of a minimum of 5 sentences on WHY some people hear Laurel and some people hear Yanny • DUE BY THE END OF CLASS!

  35. PhysiFacts 6.2 5/17 • 1. Define specific heat. • 2. Transfer of energy through the movement of matter = • 3. Transfer of energy through direct contact = • 4. Transfer of energy in the form of waves =

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