1. Chapter 22 Objectives Describe reflection, refraction, diffraction, and interference. Compare destructive interference with constructive interference. Describe resonance, and give examples. Section 3 Wave Interactions

2. Chapter 22 Reflection Reflection happens when a wave bounces back after hitting a barrier. Light waves reflecting off an object allow you to see that object. A reflected sound wave is called an echo. Waves are not always reflected when they hit a barrier. A wave is transmitted through a substance when it passes through the substance. Section 3 Wave Interactions

3. Chapter 22

4. http://www.acoustics.salford.ac.uk/schools/teacher/lesson3/flash /whiteboardcomplete.swf

5. Chapter 22 Refraction Refraction is the bending of a wave as the wave pass from one medium to another at an angle. 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. Section 3 Wave Interactions

6. Chapter 22

7. http://www.acoustics.salford.ac.uk/schools/teacher/lesson3/flash /whiteboardcomplete.swf

8. Chapter 22 Diffraction Diffraction is the bending of waves around a barrier or through an opening. The amount of diffraction of a wave depends on its wavelength and the size of the barrier or opening the wave encounters. Section 3 Wave Interactions

9. Chapter 22

10. http://www.acoustics.salford.ac.uk/schools/teacher/lesson3/flash /whiteboardcomplete.swf

11. Chapter 22 Section 3 Wave Interactions

12. Chapter 22 Interference, continued 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. In a standing wave, certain parts of the wave are always at the rest position because of total destructive interference. Other parts have a large amplitude because of constructive interference. Section 3 Wave Interactions

13. Chapter 22 Interference, continued The frequencies at which standing waves form are called resonant frequencies. Resonance happens when an object vibrating at or near the resonant frequency of a second object causes the second object to vibrate. An example of resonance is shown on the next slide. Section 3 Wave Interactions

14. Chapter 22 http://www.youtube.com/watch?feature=player_detailpage&v =xox9BVSu7Ok http://www.youtube.com/watch?v=oXV45t6wlWU