| I've done it with a microwave and some marshmallows (I taught this lab to some first year college students long ago when I spent a term as a college physics instructor). It's similar to tzs' method below, in that you have to know the frequency of the microwave's radiation, so it's not entirely satisfactory. But, given that, it's a really nice demonstration of standing waves with a cool result to calculate. The method is to cut a bunch of marshmallows in to small chunks (or just buy mini-marshmallows), spread them on a tray in a microwave and turn it on. After a while, you'll see that the marshmallows are bubbling up in some spots, and not cooking very much at all in others. Measuring the distance between either the lows or the highs gives you the wavelength of the standing wave. Given that wavelength and the frequency of the microwave radiation, you can calculate the speed of light. I'm going to punt on it and leave the calculation up to the reader, mostly because I haven't thought about this in 15 years or so and I'm sure I'd miss a factor of 2 somewhere:). Also, this will not work unless you can get a microwave where you can turn the turntable (the rotating plate thingy) off. Most microwaves didn't have a turntable in the early 90s, but this isn't true any more. |
EDIT: http://www.youtube.com/watch?v=9O2Keu6o3i0