bob p wrote:Marshmallows? Please do tell.
If you've got the marshmallows, I could use a PM-1.5 and an under-sized power resistor to boil some water for hot chocolate...
The oven works by creating a standing wave inside the oven. I believe the frequency is about optimum to excite water molecules, and the friction as they move causes the heating (another story, but the hershey bar in the pocket of a guy on a flightline standing in front of a jet fighter's radome is pretty cool, but probably fabricated ((at some flightline's they have to drink a qt of water every 20 min to stay hydrated; I doubt his hershey bar would have survuved, but anyway)))
So you take the tray out, so it doesn't rotate, and put a plate of marshmallows in. 'Nuke' it until they just start to melt, and measure the distance between the melted pits. On average (or more likely rms?) they should equal the half wavelength of the mocrowave frequency printed on the back.
Every time I remember this, I don't have any marshmallows around to actually try it.
[edit: I just looked this up, and evidently you're calculating the speed of light (3.0 X 10^8 m/sec, so if velocity=wavelength X frequency, you take the frequency printed on the back (it says usually 2450MHz) and multiply by twice the distance measured (the half wavelength) in meters and you should get close to the speed of light.]