1. Interference and Doppler Effect This may be tough so pay attention

2. Interference Waves that encounter each other engage in interference Imagine dropping two rocks at the same time into a pool The wave patterns interfere with each other

3. Interference Constructive Interference – when the waves overlap each other, which increases the amplitude Destructive Interference – when the waves oppose each other, which then causes them to cancel each other out

4. Interference Waves that cancel each other out are “out-of- phase”. For the example of light, it becomes dark. Waves that add to each other are “in phase”. The light becomes stronger

5. Doppler Effect Sources of waves, whether light or sound, can be moving. For a sound wave, this movement will cause a change in the frequency heard from the source. The siren of a firetruck approaching you will have a higher frequency than if the firetruck is at rest. The firetruck moving away from you will have a lower frequency than at rest as well.

6. Doppler Effect

8. Try some of these problems

9. Shockwaves When something moves faster than the speed of the wave it’s producing (sound in this example), it can produce a shockwave. The crests of the soundwaves produced overlap and create a cone. Once you are inside the cone, you encounter the sonicboom Sonic booms and breaking the sound barrier are not related. A plane that broke the sound barrier can make a sonic boom an hour after doing so.

11. Sonic Boom Video on sonic booms

12. Book Problems Pg 388 # 12, 15, 16, 19, 32 William was here you also have the best chair