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WAVES

WAVES. Waves. A wave is any disturbance that transmits ENERGY through matter and space. Waves carry energy NOT matter. SIM. Kinds of Waves. Longitudinal Wave The material that the wave is in vibrates back and forth along the path that the wave travels. SIM. Kinds of Waves.

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WAVES

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  1. WAVES

  2. Waves • A wave is any disturbance that transmits ENERGY through matter and space. • Waves carry energy NOT matter. SIM

  3. Kinds of Waves • Longitudinal Wave • The material that the wave is in vibrates back and forth along the path that the wave travels. SIM

  4. Kinds of Waves • Transverse Wave • The material that the wave is in moves perpendicular (at right angles) to the direction that the wave is traveling. SIM

  5. Longitudinal Waves • Compression • Section of a longitudinal wave where the particles are crowded together • Rarefaction • Section of a longitudinal wave where the particles are less crowded than normal

  6. SIM

  7. Transverse Waves SIM • Crests • The highest point in a transverse wave. • Troughs • The lowest point in a transverse wave.

  8. Crest and Trough

  9. Amplitude • Amplitude • Maximum distance the wave vibrates from its rest position SIM

  10. Which one of these waves has a larger amplitude?

  11. Wavelength • Wavelength (λ) • The distance from any point on one wave to that same point on the next wave λ SIM SIM2 λ

  12. The wavelength of a longitudinal wave can be measured as the distance between the center of two compressions or rarefactions.

  13. Which one of these waves has a larger wavelength (λ)?

  14. Frequency • Frequency • The number of waves (or cycles) produced in a given amount of time SIM

  15. Which one of these waves has a higher frequency?

  16. Review

  17. Reflection • Reflection • When a wave bounces back after striking a barrier SIM SIM2

  18. Refraction • Refraction • The bending of a wave as it passes at an angle from one material (medium) to another. SIM

  19. Diffraction • Diffraction • The bending of waves around a barrier or through an opening. SIM SIM2

  20. Interference • Interference is the result of two or more waves overlapping. • Constructive Interference • Occurs when the crests of one wave overlap the crests of another wave OR the troughs of the waves overlap

  21. Interference • Destructive Interference • Occurs when the crests of one wave and the troughs of another wave overlap

  22. Interference SIM

  23. Standing Waves • Standing wave SIM • A wave that forms a stationary pattern. • Portions of the wave do not move and other portions have a large amplitude • At rest= total destructive interference • Large amplitude=constructive interference.

  24. (SIM1) (SIM2) Sound waves are reflected at a boundary.

  25. Sound waves are refracted at a boundary.

  26. Interference. • Constructive interference • Destructive interference

  27. Here’s what is occurring. (SIM1) (SIM2) SIM - Interference

  28. Changing separation distance. Multiple sound sources interfere (SIM)

  29. Changing source frequency. Multiple sound sources interfere.

  30. What is a Medium? • A substance through which a wave can travel • Water • People • Air • Coiled wire

  31. What is a Mechanical Wave? • A wave that requires a medium • Examples: • Sound • Water

  32. Resonance • Objects have resonant frequencies • An object vibrating at the resonant frequency of a second object causes the second object to vibrate too! SIM - Resonance

  33. Speed of Sound SIM • Lightening/Thunder

  34. What Effects The Speed of Sound? • Medium

  35. What Effects The Speed of Sound? SIM • Temperature • As the temperature rises, the sound travels faster!

  36. Pitch • How high or low you perceive a sound to be • Determined by the frequency High Pitch Low Pitch

  37. Ultrasonic • Sounds with frequencies that are higher than 20,000 Hz • Infrasonic- • Sounds with frequencies that are lower than 20 Hz

  38. Volume • Decibel (dB) - unit to express volume • Exposure to sounds above 85 dB causes hearing loss SIM SIM - dB

  39. What is an Ultrasound? Ultrasound Simulation

  40. Beat Frequency • Two waves with similar frequencies alternate constructive/destructive interference • Causes sound to alternate loud and soft SIM

  41. Beating Frequency (SIM1) (SIM2)

  42. Beating Frequency Applet 2 Beating Frequency Applet 3

  43. Sound from: A stationary object A moving object SIM – Doppler Effect Labeled SIM – Hear Doppler SIM – Doppler/hear police siren SIM – Doppler/see police siren (SIM1) (SIM2)

  44. Final Note: Mechanical waves and Electromagnetic Waves are different!

  45. Sources:Bloomfield, How Things Work.Krauskopf & Beiser, The Physical Universe. 10th ed. Tillery, Physical Science.www.physicsclassroom.com

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