1. Wave Interactions Reflection, Refraction, Diffraction, Interference and Resonance

2. Which way does a ball bounce? • Wet a tennis ball and complete the following tests: • Roll it perpendicular to the wall • Roll it at an angle

3. Reflection • Reflection happens when a wave hits a surface through which it cannot pass.

4. Angles of Incidence and Reflection Normal Reflected Wave Incident Wave

5. The Law of Reflection • The angle of incidence is equal to the angle of reflection • All waves obey this law

6. Refraction • When waves enter a new medium, the waves change speed • When (and only when) the wave enters at an angle, refraction occurs • Part of the wave changes speed first • Wave becomes bent Air Water

7. REFRACTION

8. Refraction

9. Diffraction • When a wave moves around a barrier or through an opening, it bends and spreads out

10. These three (reflection, refraction, and diffraction) are how waves change direction

11. Cool Wave Oddities • Interference: when waves meet and interact, interference occurs • There are two types of interference • Constructive • Destructive

12. Cool Wave Oddities

13. Cool Wave Oddities

14. Cool Wave Oddities • Resonance: all objects have a natural frequency, and when force is applied at this particular frequency, constructive interference occurs • The amplitude of the vibration is continually reinforced until… • Catastrophe! • Or sometimes something useful happens… • http://www.youtube.com/watch?v=Qf0t4qIVWF4 plate • https://www.youtube.com/watch?v=LV_UuzEznHs vibration table • http://www.youtube.com/watch?v=cPALfz-6pnQ wine glass