1. Wave Interactions
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2. Announcement
Homework 1 should be in by tomorrow and the lab is due in next Wednesday.
We will have our first quiz on Wednesday that will be based on the homework problems.

3. Goal of the class
To understand superposition of waves. To understanding standing waves, nodes and antinodes.
Question of the Day: What happens to reflected waves at a boundary?
Previous Answer: We calculate the velocity of a wave by the formula:
Previous question: How do we calculate the velocity of a wave?
Label equation if needed

4. Wave Interference
The disturbances of waves are superimposed when they come together—a phenomenon called superposition.

5. Wave Interference
As a result of superposition of waves, interference can be observed. Interference is an effect caused by two or more waves. Waves can interfere constructively or destructively.

6. Wave Interference
The superposition of most waves produces a combination of constructive and destructive interference and can vary from place to place and time to time.
Show a demo of all these things with the big slinky

7. Reflections Reflections can occur when waves meet a boundary.
At a free boundary the waves are reflected.
At a fixed boundary the waves are reflected and inverted

8. Standing Waves
If two waves with the same amplitude and wavelength travel in opposite directions they alternate between constructive and destructive interference. The resultant looks like a wave standing in place and, thus, is called a standing wave.
Label nodes and antinodes.
Node = amp remains 0
Antinode = biggest amplitude, halfway between nodes.
The name suggets the wave isn’t moving, but it clearly is.

9. Standing Waves Nodes are points of no motion in standing waves.
An antinode is the location of maximum amplitude of a standing wave.
Draw waves for each!

10. Standing Waves
Only certain frequencies produce standing waves on a fixed string. The wavelength of these standing waves depends on the string length. Possible wavelengths include:
Draw waves for each!
2L, L, 2/3 L etc

11. Homework Read chapter 11 – Section 4
Questions on P394 Q36, 39, 43, 45, 47, 50