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Chapter 15 S1


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Chapter 15 S1

  1. 1. Chapter 15…… The Nature of Waves...
  2. 2. Waves carry energy. Remember that energy is the ability to do work or to cause a change. A wave is a traveling disturbance that carries energy from one place to another .
  3. 3. Waves are the result of kinetic energy b/c motion causes the waves. The energy carried by the waves is also kinetic because the wave is moving .
  4. 4. Cork Demo :
  5. 5. The cork did not move across the pan of water, because the water particles in which the cork was floating did not move forward with the wave that was created by the pencil.
  6. 6. The water particles rose and fell as the wave passed over them but did not move forward.
  7. 7. Since the water particles did not move, the question is, what did move??? Energy Moved
  8. 8. The energy came from the pencil being pushed up and down in the water. Remember that a wave is a traveling disturbance that carries energy from one place to another.
  9. 9. An object that is vibrating is moving, and a moving object has energy …what kind?? ___________ Energy was given to the rope by moving your hand. Wind blowing back and forth over the ocean creates ocean waves. The matter that a wave travels through is called a medium .
  10. 10. Water is a medium for ocean waves, the rope was a medium for the waves we created, and air is a medium for sound waves. There are 2 main types of waves: Transverse waves, and Longitudinal waves. Transverse waves look like: Longitudinal waves look like:
  11. 11. Waves that require a medium are Mechanical waves Waves that do not depend on a medium are electromagnetic waves.
  12. 12. Properties of Waves Section 2
  13. 13. Trough Crest Amplitude Amplitude
  14. 14. The larger the amplitude, the more energy there is. The shorter the wave length the more energy there is.
  15. 15. <ul><li>Frequency is the number of waves produced in a given amount of time. Frequency is usually expressed in hertz (Hz). One hertz equals one wave per second. </li></ul>
  16. 16. <ul><li>If the amplitudes are equal, high-frequency waves carry more energy than low-frequency waves. </li></ul>WHY?
  17. 17. <ul><li>Wave Speed is the speed at which a wave travels. </li></ul><ul><li>Wave speed can be calculated using wavelength and frequency, by using the wave equation, which is shown below: </li></ul><ul><li>Wave speed = wavelength x frequency </li></ul>
  18. 18. <ul><li>The wave speed of a wave in a certain medium is the same no matter what the wavelength is. So, the wavelength and frequency depend on the wave speed. </li></ul>
  19. 19. Wave Interactions Section 3
  20. 20. <ul><li>Reflection happens when a wave bounces back after hitting a barrier. </li></ul><ul><li>Light waves reflecting off an object allow you to see that object. </li></ul><ul><li>A reflected sound wave is called an echo . </li></ul>
  21. 21. <ul><li>Waves are not always reflected when they hit a barrier. A wave is transmitted through a substance when </li></ul><ul><li>it passes through </li></ul><ul><li>the substance . </li></ul>
  22. 22. <ul><li>Refraction is the bending of a wave as the wave pass from one medium to another at an angle. </li></ul>
  23. 23. <ul><li>When a wave moves from one medium to another, the wave’s speed and wavelength changes. As a result, the wave bends and travels in a new direction. </li></ul>
  24. 24. <ul><li>Refraction of Different Colors When light waves from the sun pass through a water droplet or a prism, the light is refracted. </li></ul>
  25. 25. <ul><ul><li>But the different colors in sunlight are refracted by different amounts, so the light is spread out into its separate colors. </li></ul></ul>
  26. 26. <ul><li>Diffraction is the bending of waves around a barrier or through an opening. </li></ul>
  27. 27. <ul><li>Interference is the result of two or more waves overlapping. </li></ul>
  28. 28. <ul><li>Constructive Interference happens when the crests of one wave overlap with the crests of another wave or waves. The troughs of the waves also overlap. </li></ul><ul><li>The result is a new wave that has a larger amplitude than the original waves had. </li></ul>
  29. 30. Destructive Interference happens when the crests of one wave and the troughs of another wave overlap. When the waves involved in destructive interference have the same amplitude and meet each other at just the right time, the result is no wave at all.
  30. 31. Standing Waves are waves that appear to be standing still . A standing wave only looks as if it is standing still. Waves are actually going in both directions.
  31. 32. Resonance happens when an object vibrating at or near the resonant frequency of a second object causes the second object to vibrate.