Having read the wonderful book How to Teach Physics to Your Dog
by Union College professor Chad Orzel (post to come), which talks about the conundrums posed by lighting behaving as both wave and particle, I decided to do a series of labs dealing with waves and leading up to some demonstrations of wave/particle duality. We started out looking at the interference pattern created by splitting a laser beam (again, post and photos to come). But then I decided it would be helpful to go back and look at plain wave behavior. So I backtracked and did two simple demonstrations of waves -- one with water, one with sound.
For the water demonstration I made a very crude approximation of a "ripple tank." I took a shallow, dark colored plastic storage box, filled it with water, and created wave patterns with two spoons. We soon found that shining a light directly on the box made it easier to see the waves via the shadows they made. Although one source suggested tapping the water with the back of the spoons, we also found that we got better results by scooping up a little water and pouring back into the tank.
We observed how one wave moved away from the source (the drip) and then bounced back off the walls of the tank. Two simultaneous waves intersected and created a pattern with stronger crests and troughs (highs and lows) where they either added together or canceled each other out.
Here's a video of a real ripple tank courtesy of the Carleton University's YouTube Channel:
Stay tuned for Wave Lab Part 2: Sound Waves, coming soon!
