This week was a short week about a complicated concept.
Waves can cancel and reinforce. (This is called interference.)
When two waves with different shapes meet, you can just add the shapes directly on top of each other to figure out the combined pattern.
You should be able to recognize the interference pattern of a double slit and explain the physics behind those images.
Waves can be found in sound, light, and on a string
Standing waves happen when they bounce back and forth within a tube (or on a string) - this is how musical instruments work. You should be able to identify the harmonic number of a standing wave.